An acoustic piano usually has a protective wooden case surrounding the soundboard and metal strings, which are strung under great tension on a heavy metal frame. Pressing one or more keys on the piano's keyboard causes a padded hammer (typically padded with firm felt) to strike the strings. The hammer rebounds from the strings, and the strings continue to vibrate at their resonant frequency. These vibrations are transmitted through a bridge to a soundboard that amplifies by more efficiently coupling the acoustic energy to the air. When the key is released, a damper stops the strings' vibration, ending the sound. Notes can be sustained, even when the keys are released by the fingers and thumbs, by the use of pedals at the base of the instrument. The sustain pedal enables pianists to play musical passages that would otherwise be impossible, such as sounding a 10-note chord in the lower register and then, while this chord is being continued with the sustain pedal, shifting both hands to the treble range to play a melody and arpeggios over the top of this sustained chord. Unlike the pipe organ and harpsichord, two major keyboard instruments widely used before the piano, the piano allows gradations of volume and tone according to how forcefully a performer presses or strikes the keys.
 

Most modern pianos have a row of 88 black and white keys, 52 white keys for the notes of the C major scale (C, D, E, F, G, A and B) and 36 shorter black keys, which are raised above the white keys, and set further back on the keyboard. This means that the piano can play 88 different pitches (or "notes'), going from the deepest bass range to the highest treble. The black keys are for the "accidentals" (F♯/G♭, G♯/A♭, A♯/B♭, C♯/D♭, and D♯/E♭), which are needed to play in all twelve keys. More rarely, some pianos have additional keys (which require additional strings). Most notes have three strings, except for the bass that graduates from one to two. The strings are sounded when keys are pressed or struck, and silenced by dampers when the hands are lifted from the keyboard. Although an acoustic piano has strings, it is usually classified as a percussion instrument rather than as a stringed instrument, because the strings are struck rather than plucked (as with a harpsichord or spinet); in the Hornbostel–Sachs system of instrument classification, pianos are considered chordophones. There are two main types of piano: the grand piano and the upright piano. The grand piano is used for Classical solos, chamber music, and art song, and it is often used in jazz and pop concerts. The upright piano, which is more compact, is the most popular type, as it is a better size for use in private homes for domestic music-making and practice.
 

During the 1800s, influenced by the musical trends of the Romantic music era, innovations such as the cast iron frame (which allowed much greater string tensions) and aliquot stringing gave grand pianos a more powerful sound, with a longer sustain and richer tone. In the nineteenth century, a family's piano played the same role that a radio or phonograph played in the twentieth century; when a nineteenth-century family wanted to hear a newly published musical piece or symphony, they could hear it by having a family member play it on the piano. During the nineteenth century, music publishers produced many musical works in arrangements for piano, so that music lovers could play and hear the popular pieces of the day in their home. The piano is widely employed in classical, jazz, traditional and popular music for solo and ensemble performances, accompaniment, and for composing, songwriting and rehearsals. Although the piano is very heavy and thus not portable and is expensive (in comparison with other widely used accompaniment instruments, such as the acoustic guitar), its musical versatility (i.e., its wide pitch range, ability to play chords with up to 10 notes, louder or softer notes and two or more independent musical lines at the same time), the large number of musicians and amateurs trained in playing it, and its wide availability in performance venues, schools and rehearsal spaces have made it one of the Western world's most familiar musical instruments. With technological advances, amplified electric pianos (1929), electronic pianos(1970s), and digital pianos (1980s) have also been developed. The electric piano became a popular instrument in the 1960s and 1970s genres of jazz fusion, funk music and rock music
 

The piano was founded on earlier technological innovations in keyboard instruments. Pipe organs have been used since Antiquity, and as such, the development of pipe organs enabled instrument builders to learn about creating keyboard mechanisms for sounding pitches. The first string instruments with struck strings were the hammered dulcimers, which were used since the Middle Ages in Europe. During the Middle Ages, there were several attempts at creating stringed keyboard instruments with struck strings. By the 17th century, the mechanisms of keyboard instruments such as the clavichord and the harpsichord were well developed. In a clavichord, the strings are struck by tangents, while in a harpsichord, they are mechanically plucked by quills when the performer depresses the key. Centuries of work on the mechanism of the harpsichord in particular had shown instrument builders the most effective ways to construct the case, soundboard, bridge, and mechanical action for a keyboard intended to sound strings.
 

The invention of the piano is credited to Bartolomeo Cristofori (1655–1731) of Padua, Italy, who was employed by Ferdinando de' Medici, Grand Prince of Tuscany, as the Keeper of the Instruments. Cristofori was an expert harpsichord maker, and was well acquainted with the body of knowledge on stringed keyboard instruments. He used his knowledge of harpsichord keyboard mechanisms and actions to help him to develop the first pianos. It is not known exactly when Cristofori first built a piano. An inventory made by his employers, the Medici family, indicates the existence of a piano by the year 1700; another document of doubtful authenticity indicates a date of 1698. The three Cristofori pianos that survive today date from the 1720s.^[Cristofori named the instrument un cimbalo di cipresso di piano e forte ('a keyboard of cypress with soft and loud'), abbreviated over time as pianoforte, fortepiano, and later, simply, piano.

While the clavichord allowed expressive control of volume and sustain, it was too quiet for large performances in big halls. The harpsichord produced a sufficiently loud sound, especially when a coupler was used to sound both manuals of a two-manual harpsichord, but it offered no dynamic or accent-based expressive control over each note. A harpsichord could not produce a variety of dynamic levels from the same keyboard during a musical passage (although a harpischord with two manuals could be used to alternate between two different stops (settings on the harpsichord which determined which set of strings are sounded), which could include a louder stop and a quieter stop). The piano offered the best features of both instruments, combining the ability to play loudly and perform sharp accents, which enabled the piano to project more during piano concertos and play in larger venues, with dynamic control that permitted a range of dynamics, including soft, quiet playing.
 

Cristofori's great success was solving, with no known prior example, the fundamental mechanical problem of designing a stringed keyboard instrument in which the notes are struck by a hammer. The hammer must strike the string, but not remain in contact with it, because this would damp the sound and stop the string from vibrating and making sound. This means that after striking the string, the hammer must be lifted or raised off the strings. Moreover, the hammer must return to its rest position without bouncing violently, and it must return to a position in which it is ready to play almost immediately after its key is depressed so the player can repeat the same note rapidly. Cristofori's piano action was a model for the many approaches to piano actions that followed in the next century. Cristofori's early instruments were made with thin strings, and were much quieter than the modern piano, but they were much louder and with more sustain in comparison to the clavichord—the only previous keyboard instrument capable of dynamic nuance via the weight or force with which the keyboard is played.

In the period from about 1790 to 1860, the Mozart-era piano underwent tremendous changes that led to the modern form of the instrument. This revolution was in response to a preference by composers and pianists for a more powerful, sustained piano sound, and made possible by the ongoing Industrial Revolution with resources such as high-quality piano wire for strings, and precision casting for the production of massive iron frames that could withstand the tremendous tension of the strings. Over time, the tonal range of the piano was also increased from the five octaves of Mozart's day to the seven octave (or more) range found on modern pianos.
 

Early technological progress in the late 1700s owed much to the firm of Broadwood. John Broadwood joined with another Scot, Robert Stodart, and a Dutchman, Americus Backers, to design a piano in the harpsichord case—the origin of the "grand". They achieved this in about 1777. They quickly gained a reputation for the splendour and powerful tone of their instruments, with Broadwood constructing pianos that were progressively larger, louder, and more robustly constructed. They sent pianos to both Joseph Haydn and Ludwig van Beethoven, and were the first firm to build pianos with a range of more than five octaves: five octaves and a fifth during the 1790s, six octaves by 1810 (Beethoven used the extra notes in his later works), and seven octaves by 1820. The Viennese makers similarly followed these trends; however the two schools used different piano actions: Broadwoods used a more robust action, whereas Viennese instruments were more sensitive.
 

By the 1820s, the center of piano innovation had shifted to Paris, where the Pleyel firm manufactured pianos used by Frédéric Chopin and the Érard firm manufactured those used by Franz Liszt. In 1821, Sébastien Érard invented the double escapement action, which incorporated a repetition lever (also called the balancier) that permitted repeating a note even if the key had not yet risen to its maximum vertical position. This facilitated rapid playing of repeated notes, a musical device exploited by Liszt. When the invention became public, as revised by Henri Herz, the double escapement action gradually became standard in grand pianos, and is still incorporated into all grand pianos currently produced in the 2000s. Other improvements of the mechanism included the use of firm felt hammer coverings instead of layered leather or cotton. Felt, which was first introduced by Jean-Henri Pape in 1826, was a more consistent material, permitting wider dynamic ranges as hammer weights and string tension increased. The sostenuto pedal (see below), invented in 1844 by Jean-Louis Boisselot and copied by the Steinway firm in 1874, allowed a wider range of effects, such as playing a 10 note chord in the bass range, sustaining it with the pedal, and then moving both hands over to the treble range to play a two-hand melody or sequence of arpeggios.
 

One innovation that helped create the powerful sound of the modern piano was the use of a massive, strong, cast iron frame. Also called the "plate", the iron frame sits atop the soundboard, and serves as the primary bulwark against the force of string tension that can exceed 20 tons (180 kilonewtons) in a modern grand. The single piece cast iron frame was patented in 1825 in Boston by Alpheus Babcock, combining the metal hitch pin plate (1821, claimed by Broadwood on behalf of Samuel Hervé) and resisting bars (Thom and Allen, 1820, but also claimed by Broadwood and Érard). Babcock later worked for the Chickering & Mackays firm who patented the first full iron frame for grand pianos in 1843. Composite forged metal frames were preferred by many European makers until the American system was fully adopted by the early 20th century. The increased structural integrity of the iron frame allowed the use of thicker, tenser, and more numerous strings. In 1834, the Webster & Horsfal firm of Birmingham brought out a form of piano wire made from cast steel; according to Dolge it was "so superior to the iron wire that the English firm soon had a monopoly." But a better steel wire was soon created in 1840 by the Viennese firm of Martin Miller, and a period of innovation and intense competition ensued, with rival brands of piano wire being tested against one another at international competitions, leading ultimately to the modern form of piano wire.
 

Other important advances included changes to the way the piano is strung, such as the use of a "choir" of three strings rather than two for all but the lowest notes, and the implementation of an over-strung scale, in which the strings are placed in two separate planes, each with its own bridge height. (This is also called cross-stringing. Whereas earlier instruments' bass strings were a mere continuation of a single string plane, over-stringing placed the bass bridge behind and to the treble side of the tenor bridge area. This crossedthe strings, with the bass strings in the higher plane.) This permitted a much narrower cabinet at the "nose" end of the piano, and optimized the transition from unwound tenor strings to the iron or copper-wrapped bass strings. Over-stringing was invented by Pape during the 1820s, and first patented for use in grand pianos in the United States by Henry Steinway, Jr. in 1859.
 

Some piano makers developed schemes to enhance the tone of each note. Julius Blüthner developed Aliquot stringing in 1893 as well as Pascal Taskin (1788), and Collard & Collard (1821). These systems were used to strengthen the tone of the highest register of notes on the piano, which up till this time were viewed as being too weak-sounding. Each used more distinctly ringing, undamped vibrations of sympathetically vibrating strings to add to the tone, except the Blüthner Aliquot stringing, which uses an additional fourth string in the upper two treble sections. While the hitchpins of these separately suspended Aliquot strings are raised slightly above the level of the usual tri-choir strings, they are not struck by the hammers but rather are damped by attachments of the usual dampers. Eager to copy these effects, Theodore Steinway invented duplex scaling, which used short lengths of non-speaking wire bridged by the "aliquot" throughout much of upper the range of the piano, always in locations that caused them to vibrate sympathetically in conformity with their respective overtones—typically in doubled octaves and twelfths. The mechanical action structure of the upright piano was invented in London, England in 1826 by Robert Wornum, and upright models became the most popular model. Upright pianos took less space than a grand piano, and as such they were a better size for use in private homes for domestic music-making and practice.
 

Some early pianos had shapes and designs that are no longer in use. The square piano (not truly square, but rectangular) was cross strung at an extremely acute angle above the hammers, with the keyboard set along the long side. This design is attributed to Gottfried Silbermann or Christian Ernst Friderici on the continent, and Johannes Zumpe or Harman Vietor in England, and it was improved by changes first introduced by Guillaume-Lebrecht Petzold in France and Alpheus Babcock in the United States. Square pianos were built in great numbers through the 1840s in Europe and the 1890s in the United States, and saw the most visible change of any type of piano: the iron-framed, over-strung squares manufactured by Steinway & Sons were more than two-and-a-half times the size of Zumpe's wood-framed instruments from a century before. Their overwhelming popularity was due to inexpensive construction and price, although their tone and performance were limited by narrow soundboards, simple actions and string spacing that made proper hammer alignment difficult.
 

The tall, vertically strung upright grand was arranged like a grand set on end, with the soundboard and bridges above the keys, and tuning pins below them. The term was later revived by many manufacturers for advertising purposes. "Giraffe pianos", "pyramid pianos" and "lyre pianos" were arranged in a somewhat similar fashion, using evocatively shaped cases. The very tall cabinet piano was introduced about 1805 and was built through the 1840s. It had strings arranged vertically on a continuous frame with bridges extended nearly to the floor, behind the keyboard and very large sticker action. The short cottage upright or pianino with vertical stringing, made popular by Robert Wornum around 1815, was built into the 20th century. They are informally called birdcage pianos because of their prominent damper mechanism. The oblique upright, popularized in France by Roller & Blanchet during the late 1820s, was diagonally strung throughout its compass. The tiny spinet upright was manufactured from the mid-1930s until recent times. The low position of the hammers required the use of a "drop action" to preserve a reasonable keyboard height. Modern upright and grand pianos attained their present, 2000-era forms by the end of the 19th century. While improvements have been made in manufacturing processes, and many individual details of the instrument continue to receive attention, and a small number of acoustic pianos are produced with MIDI recording and sound module-triggering capabilities, the 19th century was the era of the most dramatic innovations and modifications of the instrument.
 

Modern acoustic pianos have two basic configurations, the grand piano and the upright piano, with various styles of each. There are also specialized and novelty pianos, electric pianos based on electromechanical designs, electronic pianos that synthesize piano-like tones using oscillators, and digital pianos using digital samples of acoustic piano sounds.

In grand pianos, the frame and strings are horizontal, with the strings extending away from the keyboard. The action lies beneath the strings, and uses gravity as its means of return to a state of rest. There are many sizes of grand piano. A rough generalization distinguishes the concert grand (between 2.2 and 3 meters [7 ft 3 in–9 ft 10 in]) from the parlor grand or boudoir grand (1.7 to 2.2 meters [5 ft 7 in–7 ft 3 in]) and the smaller baby grand (around 1.5 meters [4 ft 11 in]).
 

All else being equal, longer pianos with longer strings have larger, richer sound and lower inharmonicity of the strings. Inharmonicity is the degree to which the frequencies of overtones (known as partials or harmonics) sound sharp relative to whole multiples of the fundamental frequency. This results from the piano's considerable string stiffness; as a struck string decays its harmonics vibrate, not from their termination, but from a point very slightly toward the center (or more flexible part) of the string. The higher the partial, the further sharp it runs. Pianos with shorter and thicker string (i.e., small pianos with short string scales) have more inharmonicity. The greater the inharmonicity, the more the ear perceives it as harshness of tone.
 

The inharmonicity of piano strings requires that octaves be stretched, or tuned to a lower octave's corresponding sharp overtone rather than to a theoretically correct octave. If octaves are not stretched, single octaves sound in tune, but double—and notably triple—octaves are unacceptably narrow. Stretching a small piano's octaves to match its inherent inharmonicity level creates an imbalance among all the instrument's intervallic relationships, not just its octaves. In a concert grand, however, the octave "stretch" retains harmonic balance, even when aligning treble notes to a harmonic produced from three octaves below. This lets close and widespread octaves sound pure, and produces virtually beatless perfect fifths. This gives the concert grand a brilliant, singing and sustaining tone quality—one of the principal reasons that full-size grands are used in the concert hall during piano concerto with orchestra. Smaller grands satisfy the space and cost needs of domestic use; as well, they are used in some small teaching studios and smaller performance venues.
 

Upright pianos, also called vertical pianos, are more compact because the frame and strings are vertical. Upright pianos are generally less expensive than grand pianos. Upright pianos are widely used in churches, community centers, schools, music conservatories and university music programs as rehearsal and practice instruments, and they are popular models for in-home purchase. The hammers move horizontally, and return to their resting position via springs, which are susceptible to degradation. Upright pianos with unusually tall frames and long strings are sometimes called upright grand pianos. Some authors classify modern pianos according to their height and to modifications of the action that are necessary to accommodate the height.

The toy piano, introduced in the 19th century, is a small piano-like instrument, that generally uses round metal rods to produce sound, rather than strings. The US Library of Congress recognizes the toy piano as a unique instrument with the subject designation, Toy Piano Scores: M175 T69. In 1863, Henri Fourneaux invented the player piano, which plays itself from a piano roll. A machine perforates a performance recording into rolls of paper, and the player piano replays the performance using pneumatic devices. Modern equivalents of the player piano include the Bösendorfer CEUS, Yamaha Disklavier and QRS Pianomation, using solenoids and MIDI rather than pneumatics and rolls. A silent piano is an acoustic piano having an option to silence the strings by means of an interposing hammer bar. They are designed for private silent practice, to avoid disturbing others. Edward Ryley invented the transposing piano in 1801. This rare instrument has a lever under the keyboard as to move the keyboard relative to the strings so a pianist can play in a familiar key while the music sounds in a different key.

The minipiano is an instrument patented by the Brasted brothers of the Eavestaff Ltd. piano company in 1934. This instrument has a braceless back, and a soundboard positioned below the keys—meaning that long metal rods pulled on the levers to make the hammers strike the strings. The first model, known as the Pianette, was unique in that the tuning pins extended through the instrument, so it could be tuned at the front.
 

The prepared piano, present in some contemporary art music from the 20th and 21st century is a piano with objects placed inside it to alter its sound, or has had its mechanism changed in some other way. The scores for music for prepared piano specify the modifications, for example instructing the pianist to insert pieces of rubber, paper, metal screws, or washers in between the strings. These either mute the strings or alter their timbre. A harpsichord-like sound can be produced by placing or dangling small metal buttons in front of the hammer. Adding an eraser between the bass strings produces a mellow, thumpy sound reminiscent of the plucked double bass. Inserting metal screws or washers can cause the piano to make a jangly sound as these metal items vibrate against the strings. In 1954 a German company exhibited a wire-less piano at the Spring Fair in Frankfurt, Germany that sold for US $238. The wires were replaced by metal bars of different alloys that replicated the standard wires when played. A similar concept is used in the electric-acoustic Rhodes piano.
 

The first electric pianos from the late 1920s used metal strings with a magnetic pickup, an amplifier and a loudspeaker. The electric pianos that became most popular in pop and rock music in the 1960s and 1970s, such as the Fender Rhodes use metal tines in place of strings and use electromagnetic pickups similar to those on an electric guitar. The resulting electrical, analogue signal can then be amplified with a keyboard amplifier or electronically manipulated with effects units. Electric pianos are rarely used in classical music, where the main usage of them is as inexpensive rehearsal or practice instruments in music schools. However, electric pianos, particularly the Fender Rhodes, became important instruments in 1970s funk and jazz fusion and in some rock music genres.
 

Electronic pianos are non-acoustic; they do not have strings, tines or hammers, but are a type of synthesizer that simulates or imitates piano sounds using oscillators and filters that synthesize the sound of an acoustic piano. They need to be connected to a keyboard amplifier and speaker to produce sound (however, some electronic keyboards have a built-in amp and speaker). Alternatively, a person can practice an electronic piano with headphones to avoid disturbing others.
 

Digital pianos are also non-acoustic and do not have strings or hammers. They use digital sampling technology to accurately reproduce the acoustic sound of each piano note. They also need to be connected to a power amplifier and speaker to produce sound (however, most digital pianos have a built-in amp and speaker). Alternatively, a person can practice with headphones to avoid disturbing others. Digital pianos can include sustain pedals, weighted or semi-weighted keys, multiple voice options (e.g., sampled or synthesized imitations of electric piano, Hammond organ, violin, etc.), and MIDI interfaces. MIDI inputs and outputs allow a digital piano to be connected to other electronic instruments or musical devices. For example, a digital piano's MIDI out signal could be connected by a patch cord to a synth module, which would allow the performer to use the keyboard of the digital piano to play modern synthesizer sounds. Early digital pianos tended to lack a full set of pedals but the synthesis software of later models such as the Yamaha Clavinova series synthesised the sympathetic vibration of the other strings (such as when the sustain pedal is depressed) and full pedal sets can now be replicated. The processing power of digital pianos has enabled highly realistic pianos using multi-gigabyte piano sample sets with as many as ninety recordings, each lasting many seconds, for each key under different conditions (e.g., there are samples of each note being struck softly, loudly, with a sharp attack, etc.). Additional samples emulate sympathetic resonance of the strings when the sustain pedal is depressed, key release, the drop of the dampers, and simulations of techniques such as re-pedalling.

A digital piano is an electronic keyboard that emulates the sound and the feel of a genuine acoustic piano. It can be differentiated from its precursor instrument – the “synthesizer” – which uses electronically produced sound waves to create specifically electronic sounds. The first digital piano commercially available was produced by Yamaha in 1983. The Clavinova YP-40 was the most notable of the releases. More of an extension of the synthesizers of the 1970s, the sounds were electronically produced using Frequency Modulation, rather than sampling technology which is used by all digital pianos today. [1] Frequency Modulation synthesis (more commonly referred to as simply “FM”) works by modulating (or changing) the frequency of an electronically produced sound wave. This results in a wide variety of tone, dependent upon the changes in frequency and a combination of other waves. [2] A sample, on the other hand, is a short digital recording that can be triggered via a MIDI instrument, such as a piano-style keyboard. [3]
 

A modern digital piano has a large bank of short digital recordings (samples) that are triggered by hitting the keys of the keyboard. Most modern digital pianos are capable of reproducing touch-sensitive play (see later). Modern digital pianos contain samples taken from a variety of genuine grand (and upright) pianos, recorded at high quality. Most digital pianos offer more than one piano sound, as well as a variety of other instrumental sounds such as electric piano, organs and strings. But it’s not just the sound you should look out for when choosing a digital piano. The build quality is massively important and can truly affect your experience of playing. It’s important to understand some of the mechanics of the acoustic instrument when exploring the features of the digital piano, so we’ll be focusing on the relevant mechanisms in this article.
 

The digital piano was developed to bring the experience of a genuine piano to a versatile, compact unit, so understanding the internal workings of the digital piano (and how it relates to the acoustic instrument) can help you choose a digital piano that feels like the real thing. The most popular manufacturers of digital pianos are Yamaha, Roland, Kawai and Casio. 

The pianoforte is a percussion instrument. We usually associate percussion with instruments that you hit, strike, bang or purposely collide, either with a stick, a beater, a key or the hand. Examples of commonly recognized percussions instruments are drums, timpani (aka kettle drum), cymbals, gongs, glockenspiels, xylophones and tambourines. The piano is played by pressing the (usually) white and black keys on the keyboard. When a key is pressed, it triggers a chain of events that ends with a felt-coated hammer, striking a string (or strings). It is this “hitting” action that classifies the piano as a percussion instrument. The acoustic piano usually has three strings per note to create a fuller tone – the hammer hits all three strings. [4] Digital pianos don’t usually have strings, but they do have the same keyboard interface as the acoustic instrument – at least, on the surface. Rather than hitting a string, the depression of the key results in contact with an electronic sensor which triggers the note. Sensors can often detect more than just “on” and “off” and many can respond to the intensity of the key press. [5] The full name of the instrument widely referred to as the “piano” is actually “pianoforte”. Pianoforte is a conjugation of two Italian words, referring to the dynamics of musical play – “piano” meaning “soft” and “forte” meaning loud. The pianoforte, therefore, is capable of playing both quietly (by pressing the key softly) and loud (by pressing the key with harder force). All digital pianos also have this ability. [6]
 

The piano is a percussion instrument that is capable of playing a wide range of dynamics (dynamics are variations in the volume of the music) – more than that of the guitar. The sound of a piano note is achieved by a hammer hitting a string (or strings). The keys of a digital pianos connect with a sensor that triggers an audio sample. Digital pianos can often recognize the velocity of the key press and respond with either loud or soft playback of the audio sample. Never buy a digital piano until you’ve tried it out. The instrument should be capable of a wide array of dynamic responses, including accurate soft and loud play.

The keyboard. The piano keyboard is the musician’s interface, providing control over the instrument. A full-sized piano has 88 keys, arranged in a regular sequence of white and black keys. A digital piano can come in a variety of sizes, but if you’re looking for an instrument that looks and feels like a genuine piano, you should demand 88, full-sized, weighted keys. The full-sized piano keyboard spans 8 octaves. The keys of an acoustic piano are traditionally made from wood, and laminated with either an ivory surface (for the white keys) or an ebony surface (for the black keys). The keys of digital pianos are usually made from plastic, although some higher-end models use real piano keys. The black keys sit in between and slightly raised from the white keys. Navigation around the keyboard is made possible from recognizing the repeated sequence of black keys, which are grouped in 2s and 3s, respectively. [7] A sequence of 2 black adjacent notes is followed by two adjacent white notes, followed by 3 black notes, followed by another 2 adjacent white notes. This arrangement is repeated throughout the entire keyboard.
 

There are 7 notes in the music “alphabet” – A, B, C, D, E, F and G, which repeat across the entire keyboard. A full octave is 8 notes apart – C to the next C, for example.

A full-sized piano has 88 keys which are a combination of white and black notes. Navigation of the keyboard is afforded by the grouping of the black notes, which are in 2s and 3rd, regularly across the entire span of the keyboard. Digital pianos use exactly the same arrangement of keys as acoustic pianos. When looking to buy a digital piano, it’s advisable to go for an 88 key model. Keyboards come in a variety of ranges from just 25-, 49- or 61-key. The larger the keyboard, the less portable it becomes, so if you’re looking for a digital piano that’s going to stay in one place, 88 keys is best.

Weighted keys. When you depress a note on an acoustic piano, there’s a mechanical chain of events that ends with a hammer that hits a string. This sequence of arms and levers gives the piano a weight that musicians have come to expect from the piano playing experience. A piano key of a grand piano operates a little like a see-saw. When you depress the key, it pivots the arm in the centre, raising a hammer attached to the other end of the wooden arm which strikes the string. The part of the key that you can commonly see is just one section of the hammered arm. Traditionally, the keys at the bottom end of the piano playing the “low” notes (the left hand side of the keyboard) have longer wooden arms than the “top” notes (played on the right hand side of the keyboard) which have shorter arms. [8] This difference in key arm lengths adds a different physical weight to the keys. The bottom keys of a grand piano are “heavier” under the fingers because they have longer arms than the top keys. Many digital pianos have weighted keys, using various mechanical means to reproduce the sensation of weight. Some of the higher-end models have a “Graded Hammer Action” which emulates the traditional grand piano by weighting the keys more heavily at the bottom end of the keyboard and more lightly at the top. If you’re looking for a digital piano with a realistic, pianistic keyboard, you should look for a model that has a “Graded Hammer Action”.
 

The keys of acoustic pianos feel heavier at the bottom end (the left hand side) and lighter at the top end of the keyboard (the right hand side). This is due to the length of the wooden arm that pivots, resulting in the hammer of the key hitting the string or strings. Many digital pianos emulate this keyboard weighting with a system called “Graded Hammer Action”. Decent weighting of the keys of a digital piano is essential. If you learn on a digital piano, you need to develop the muscle-memory required to play dynamic music, which you will only learn accurately if the keyboard feels like an acoustic piano to play.

The Hammer Mechanism. Although most digital pianos don’t have the same hammer mechanism as an acoustic piano, an understanding of the mechanics (and how they’re emulated with digital instruments) will help you to decide which piano is the best choice for you.

There are 5 essential elements to a piano key mechanism – the key, the fulcrum, the hammer, the damper and the string.

The key is the part of the mechanism that you can see, covered in ebony and ivory (or a more ethical alternative). The resting position for the key is “up”. At resting position the hammer is away from the string and the damper rests on the string to stop the string from resonating. The resting position is determined by the position of the fulcrum – effectively it sits closer to the key than to the damper, making the hammer and damper end of the key-arm longer (and thus heavier). This is where the “weight” of the key comes from.
 

When you press the key down, the fulcrum pivots the hammer arm upwards, making the hammer hit the string. At the same time, the damper lifts and stays lifted allowing the note to sustain and the strings to continue to resonate until the point at which the key is released, making the damper return to its resting position, sitting upon the string and stopping the resonation. [9] This hammer action is emulated in many ways with digital pianos. Digital pianos are generally smaller than acoustic pianos and, therefore, don’t have the internal space (or need) for the full key mechanism. The big manufacturers have developed unique methods of approximating the mechanics of a real piano, but have condensed the whole workings in half of the physical space. For example, Kawai has condensed the entire workings of the piano mechanism into the space below the key. When you release the key of an acoustic piano, there’s a light “bounce” (known as “key-off bounce”) as the mechanics of the key return to equilibrium. Kawai’s Responsive Hammer Action III device emulates the full mechanical experience of playing a real piano key, including the key-off “bounce”.  [10] Cheaper digital pianos emulate the hammer mechanism with a key, a weight and a spring. The problem with a “sprung” key is that it bounces back into the resting position too harshly, without a realistic key-off bounce. When looking to choose a digital piano, it’s useful to research the hammer response – many music shops provide a small display model of the mechanism. However, the real proof of the pudding is in the playing. If you’re familiar with how an acoustic piano feels to play, look for a keyboard that realistically emulates that. Digital pianos at the higher end have become incredibly realistic – if you have a budget of over $1500, you should expect a great keyboard build as standard. If possible, avoid buying a digital piano with “sprung” keys – the play feel will be unrealistic. Although digital pianos are triggering digital sounds, the more mechanical the actual keyboard build, the more realistic a playing experience you’ll get.

Escapement. Escapement is part of the mechanical hammer action of an acoustic piano. You’re likely to notice the term in the specification list of many digital pianos. As we know, when you press a key on an acoustic piano, it forces the hammer to hit the string. But the hammer immediately moves away from the string, even if you keep holding down the key, otherwise the hammer would remain on the string and dampen the sound. You would normally hold the key down if you are playing a long note. It’s the escapement that drops the hammer away from the string so that the note can sustain. You can feel the point at which the escapement triggers by playing a key really softly on an acoustic instrument. You’ll feel a “bump” about three quarters of the way down – this is the escapement mechanism. The escapement allows the note to sustain by moving the hammer away from the key. However, the note can’t be played again until the key has been fully released (or release just above the escapement). This is problematic if you’re playing rapidly repeated notes – especially if you’re playing them softly. Unless you play “above the escapement” you’ll have missed notes. With an acoustic piano, you learn where the escapement “bump” occurs and develop the technique of playing “above the escapement” to avoid this mechanical misfiring. With a digital piano, of course, there are usually no strings or an actual hammer. However, many of the higher range digital pianos include this escapement “bump” to emulate the feel of a real piano keyboard. [11]
 

Escapement is a mechanism that you often find in high-end digital pianos. It emulates the “escapement bump” present in the mechanical workings of an acoustic piano. Playing soft and fast can be difficult on an acoustic piano because the escapement can prevent quickly repeated notes, unless the player learns to play “above the escapement”. If you learn on a digital piano without escapement, you’ll experience problems when you sit at an acoustic instrument, unless you learn to play above the escapement. Escapement in a digital piano provides a more authentic playing experience, so if you’re looking for a digital instrument that’s as close to the real article as you can get, look for a digital piano with an escapement mechanism.

Plastic vs Wooden keys. Acoustic pianos have wooden keys. This provides weight to the key mechanism. Most digital pianos have plastic keys. However, more recently, some of the high-end model ranges have started to re-introduce wooden keys. Some manufacturers boast “real piano keys” as a selling point. But does it make any difference? To cut the argument short – yes, it does. It certainly adds to the price!
 

Early digital pianos had purely plastic, often hollow keys, that afforded very little actual “weight” to the body of the key. Any physical weight added to the key-feel was via a spring mechanism or a weight attached to the plastic key. Whilst being completely acceptable, hollow plastic keys often lack the feel of an acoustic piano. [12] Most modern, high-end piano manufacturers have moved away from the basic, hollow plastic key, developing new surface feels (sometimes referred to as “Ivory feel”) and weightier plastics that aim to emulate or even improve upon the acoustic piano feel. Matte-finish keys are commonly seen in some of the higher-end models. Matte-finish keys have been developed to prevent finger slippage, and to absorb finger perspiration, providing a better connection between finger and key. This is an innovation found only in digital pianos – acoustic piano keys tend to have a glossy finish, whether they’re ebony and ivory or an alternative wooden build. [13] Some digital pianos in the top price bracket have genuine, wooden piano keys. If you have a high budget and want an instrument close to the real thing, look for wooden keys. Plastic keys come as standard with most digital pianos. If you have a higher budget, you can look for “Ivory feel” keys. These are usually fully plastic, composite keys that have a weightier feel than a hollow plastic key, which was more common with early digital pianos. Some digital piano manufacturers have started to reintroduce “real piano keys”. These, obviously, have the most convincing piano feel but come at a considerable price premium.

The foot pedals. There are usually two foot pedals with a standard upright acoustic piano, and three foot pedals with a standard grand piano. The two pedals on an upright operate the una corda and damper operations. Digital pianos, originally, had just two pedals. More recent models, however, have a third (sostenuto) foot pedal, just like an acoustic grand. To understand what each pedal does, it’s useful to understand the role each pedal plays with an acoustic piano.
 

Una corda. The una corda pedal is situated on the left hand side of the pedal configuration. Under normal conditions, the hammer hits three strings which creates a fuller, louder tone. However, when the una corda pedal is depressed, the hammers on a grand piano move to the right, making the hammers hit just two of the strings (or more traditionally, one of the strings (hence “una corda”). The instrument, as such, produces a quieter, softer tone. Hence, the una cordapedal is more commonly referred to as the “soft” pedal. The una corda pedal plays a slightly different role with an acoustic upright piano – rather than moving the hammers to the right, the una corda pedal moves the hammers closer to the string, thus reducing the distance the hammer can travel towards the key, resulting in a softer note.
 

Damper. The damper (or sustain) pedal is on the right hand side of the pedal configuration and is the most commonly used of all the foot pedals. When a key is pressed, the hammer hits the string and the “damper” (which usually sits on the string) raises, allowing the string to resonate. When the piano key is released, the damper returns to the string and prevents further resonation. However, the damper pedal, when pressed, physically moves the damper away from all of the strings; thus permitting all of the strings to resonate whenever a key is played, resonating until the damper pedal is released or the sound has naturally decayed. Playing the piano requires sensitive use of the damper pedal – over-use creates a “muddy” sound. There are various techniques associated with damper pedal play, including “half damper” which reduces the overall effect of the fully open damper. [14] Acoustic pianos respond depending upon how far you press the damper foot pedal. A light press results in a half-sustain. Only some digital pianos are capable of this range of control – look for “damper control” in the list of specifications. 
 

Sostenuto. When there are three foot pedals, the middle one is the “sostenuto” pedal. The pedal to the left is the una corda, and the pedal to the right is the damper. The sostenuto pedal is quite rarely used. The “sostenuto” pedal operates in a similar way to the damper pedal, in that it releases the dampers from the strings. However, the sostenuto pedal lifts the damper from only the keys that are played at the time that the pedal was pressed. All following notes are played with the damper in the usual position. This creates sustain of the notes played whilst the pedal was pressed and a “staccato” effect for the following notes. The term “Staccato” means short, detached. A staccato note is played quickly and the sound dampens immediately. [16]
 

Digital piano pedals. The pedals of a digital piano emulate the acoustic instrument. However, there is no damper inside a digital instrument. Changes in the production of the sound is made possible by triggering different samples, rather than any physical changes to internal resonance. [17] With some digital pianos, the middle foot pedal can be assigned to different tasks, such as page turning for sheet music apps (on a computer tablet such as an iPad) or for changing instrumental voices. Most digital upright pianos have at least two foot pedals which operate an una corda (or soft) and a damper (or sustain) function. Una corda (or the soft pedal) produces a quieter sound. The damper pedal allows the whole instrument to resonate until the pedal is released.
 

Some digital pianos have a sostenuto pedal, which is situated in the middle of the three pedals.  Sostenuto is an effect that sustains some notes and dampens others. The middle pedal can often be assigned to perform different tasks in a digital piano. The construction of a digital upright piano. The digital upright piano consists of the keyboard unit (containing the keys, the circuitry and the speakers), attached to a permanent stand or housing unit. The keyboard unit is permanently attached to a stand unit (although most can be temporarily detached). The stand unit usually consists of a pedal board, which includes at least two foot pedals and a speaker unit, often containing multiple speakers. A digital piano is often capable of producing a variety of sampled and electronic “voices”. Most digital pianos have more than one piano sound, with a variety of room resonance settings that help transport the player to the large concert hall. Other voices commonly found with digital pianos include electric pianos (Fender Rhodes sounds), organs (such as jazz and church organs) and strings.
 

A keyboard with many voices isn’t necessarily better than one with few. If you are going to use your digital piano purely for playing piano voices, it’s worth focusing on the instruments that reproduce the best piano tone, rather than being attracted by the slightly “gimmicky” additional voices that you are unlikely to use. [18] Most digital pianos allow the user to connect at least one pair of headphones, providing “silent” operation of the instrument and allowing the player to perform without disturbing other people in the immediate vicinity. This is one of the most popular features of the digital piano over the noisy acoustic instrument. Many modern digital pianos have two headphone outputs, which is good for piano lessons. [19] Digital upright pianos have a user interface that allow the user to choose between the various features of the piano, as well as control the different on-board voices. User interfaces range widely in quality and mode. Some top-end digital pianos have LCD navigation displays that provide quick access to the piano’s main editable functions. [20] Some lower-priced digital pianos have very simple user-interfaces that have limited functionality. Most digital upright and stage pianos have volume controls that adjust the decibel output of the speakers. Digital upright pianos are furniture-style units that contain the keyboard unit and a permanent stand that houses the foot-pedals and the speakers of the instrument. The user interface of the digital piano allows you to control which instrumental voice plays, as well as providing many editable functions that dictate changes in the way that the instrument sounds.

Stage piano. A stage piano is a digital piano that comes as a single, portable unit. It has no built-in stand or housing unit and has no native foot pedals attached, although most come with a detachable damper pedal as a minimum. A collapsable X-Frame stand is most commonly used for a stage piano. Stage pianos usually contain the vast majority of the operations capable with a digital upright. They are popular with professional, touring musicians because they are designed to be easily transported. They usually have less complex user interfaces (digital screens) than digital uprights. Most modern stage pianos have an internal speaker system, although some (usually older) models require external amplification via a PA system. The keyboard build is likely to be similar or the same as digital upright pianos. However, stage pianos need to be relatively lighter in weight as they need to be transported, so sometimes have lighter internal components. Stage pianos are generally cheaper to buy than digital upright pianos, but usually offer equivalent functionality. More stage pianos do have fixable stands as additional accessories, which are worth buying if you intend to keep your stage piano for home use. [21] A stage piano is a digital piano unit with no fixed stand, designed for portability. They’re popular with professional, touring musicians. They require additional foot-pedals – most come packaged with (at least) the damper pedal, as this is the most commonly used. Stage pianos are generally cheaper to buy than digital uprights and have equivalent functionality. Most stage pianos have fixed stand units available as an optional accessory.

MIDI. MIDI is a digital protocol developed during the early 1980s which facilitates the communication of electronic instruments. The term MIDI is an acronym for Musical Instrument Digital Interface. MIDI, in itself, does not produce any sound – it is more accurately defined as a list of messages sent almost instantaneously between instruments (or recorded and stored for later reproduction). The messages are On / Off (1 / 0) commands – controlling Note on, Note off, Note/Pitch, Velocity, Pitchbend etc. These messages are sent by one instrument (or computer) and received by another which interprets those instructions using its internal component functionality.
 

MIDI information is transferred via a cable or through wireless means, such as Bluetooth. [22] The first MIDI cables were 5 pin DIN cables, which had previously been used to transmit data and audio signals. [23] This connection protocol can only carry information in one direction, so with old MIDI instruments, there was a MIDI IN and a MIDI OUT (and occasionally MIDI THRU) sockets. The Master device (sending the MIDI data) would use its MIDI OUT socket, which was connected to the MIDI IN of the receiving (or Slave) instrument. In order for the Slave instrument to send data back to the Master device (often a sequencer), its MIDI OUT connection needed to be connected to the Master’s MIDI IN. [24] More recently, USB cables have been used to transfer MIDI information between electronic instruments. A USB cable provides two way information, so only one cable is required as opposed to the two cables required with 5 pin DIN MIDI. This has been a major breakthrough in the ability for home computers to natively connect directly to electronic musical instruments. [25]
 

Bluetooth MIDI is the latest innovation in MIDI data transfer, opening up the music making functionality of mobile devices such as mobile phones and tablet computers. Bluetooth MIDI allows electronic musical instruments and interfaces to communicate wirelessly. Not only does Bluetooth allow for data transfer, but can also allow for audio transfer. This is a real breakthrough for the mobile musician, allowing a mobile app (such as Cubase or Korg Gadget) to be controlled externally, transmitting the resulting audio signal through the external speakers of the receiving instrument. [26]
 

MIDI is a digital language that allows musical instruments and music computer software to communicate. All digital pianos have some kind of MIDI interface, allowing the user to expand the capabilities of the instrument. Instruments connect together via 5 pin DIN and / or USB cables, or wirelessly via Bluetooth.

Bluetooth. Bluetooth has brought about a sea-change in how we connect appliances together and, for the music world, it has revolutionized how one instrument communicates with another. MIDI is a language of ones and zeros and doesn’t transfer audio, just data. However Bluetooth connection has changed all of that.

Now it is possible to wirelessly link your digital piano to one of the countless music-making apps available on Apple’s iOS platform. iOS is leading the way, by offering a wide array of music apps, with the likes of Steinberg and Korg heavily investing in the platform to present great, professional, mobile studio software such as Cubase and Gadget, amongst a wide expanse of others. [27] iOS devices have much lower audio latency than Android devices, so for the present, music apps for Android mainly cater to the gaming market as opposed to the serious music-maker [28]
 

The big advantage with Bluetooth is that your device doesn’t just connect to your digital piano to communicate MIDI data, but transfers digital audio as well. The iOS device connects its audio output wirelessly to the internal speaker system on your digital piano. This holds amazing connectivity potential. Some digital pianos have rather disappointing user interfaces,  providing little by way of editing the play and sound parameters of the instrument. Some keyboards – the Kawai CN27, for example, is capable of some really detailed player customizability, but has only 6 buttons and a digital display that makes navigating the potential options impossible.
 

However, the CN27 has on-board Bluetooth capability which extends to a “Virtual Technician” iPad app, allowing the user the ability to change many digital parameters that affect both the piano playing experience and the sound produced by the instrument. For example, it’s possible to change room sizes within the reverb settings, adjust foot-pedal noise, virtually raise or lower the piano lid to adjust the brightness of the overall sound, even affect tuning.
 

More and more digital pianos are built with native Bluetooth capabilities. For those that aren’t, there’s usually a Bluetooth dongle that can be fitted to facilitate Bluetooth communication between devices. Bluetooth can transmit both audio and MIDI data, making it the future of wireless connectivity for electronic musical instruments. Many modern digital pianos have native Bluetooth capability, although there are dongles available that are compatible with the most recent modes if they don’t.
 

Bluetooth allows a digital piano to connect to music-making apps (principally on Apple’s iOS platform), potentially adding vast studio-making capabilities to your existing instrument. There is a wide array of music-making apps available on Apple’s iOS platform, offering cutting edge music-production capabilities to your digital piano. It also allows the user to control detailed parameters with “Virtual Technician” apps, for digital pianos that lack a detailed user interface.

Digital, MIDI-equipped, pianos can output a stream of MIDI data, or record and play via a CD ROM or USB flash drive using MIDI format files, similar in concept to a pianola. The MIDI file records the physics of a note rather than its resulting sound and recreates the sounds from its physical properties (e.g., which note was struck and with what velocity). Computer based software, such as Modartt's 2006 Pianoteq, can be used to manipulate the MIDI stream in real time or subsequently to edit it. This type of software may use no samples but synthesize a sound based on aspects of the physics that went into the creation of a played note.
 

In the 2000s, some pianos include an acoustic grand piano or upright piano combined with MIDI electronic features. Such a piano can be played acoustically, or the keyboard can be used as a MIDI controller, which can trigger a synthesizer module or music sampler. Some electronic feature-equipped pianos such as the Yamaha Disklavier electronic player piano, introduced in 1987, are outfitted with electronic sensors for recording and electromechanical solenoids for player piano-style playback. Sensors record the movements of the keys, hammers, and pedals during a performance, and the system saves the performance data as a Standard MIDI File (SMF). On playback, the solenoids move the keys and pedals and thus reproduce the original performance. Modern Disklaviers typically include an array of electronic features, such as a built-in tone generator for playing back MIDI accompaniment tracks, speakers, MIDI connectivity that supports communication with computing devices and external MIDI instruments, additional ports for audio and SMPTE I/O, and Internet connectivity. Disklaviers have been manufactured in the form of upright, baby grand, and grand piano styles (including a nine-foot concert grand). Reproducing systems have ranged from relatively simple, playback-only models to the PRO models which record performance data at resolutions that exceed the limits of normal MIDI data. The unit mounted under the keyboard of the piano can play MIDI or audio software on its CD or floppy disk drive.
 

Pianos can have upwards of 12,000 individual parts,^[supporting six functional features: keyboard, hammers, dampers, bridge, soundboard, and strings.  Many parts of a piano are made of materials selected for strength and longevity. This is especially true of the outer rim. It is most commonly made of hardwood, typically hard maple or beech, and its massiveness serves as an essentially immobile object from which the flexible soundboard can best vibrate. According to Harold A. Conklin, the purpose of a sturdy rim is so that, "... the vibrational energy will stay as much as possible in the soundboard instead of dissipating uselessly in the case parts, which are inefficient radiators of sound."

Hardwood rims are commonly made by laminating thin, hence flexible, strips of hardwood, bending them to the desired shape immediately after the application of glue. The bent plywood system was developed by C.F. Theodore Steinway in 1880 to reduce manufacturing time and costs. Previously, the rim was constructed from several pieces of solid wood, joined and veneered, and this method continued to be used in Europe well into the 20th century. A modern exception, Bösendorfer, the Austrian manufacturer of high-quality pianos, constructs their inner rims from solid spruce, the same wood that the soundboard is made from, which is notched to allow it to bend; rather than isolating the rim from vibration, their "resonance case principle" allows the framework to more freely resonate with the soundboard, creating additional coloration and complexity of the overall sound.
 

The thick wooden posts on the underside (grands) or back (uprights) of the piano stabilize the rim structure, and are made of softwood for stability. The requirement of structural strength, fulfilled by stout hardwood and thick metal, makes a piano heavy. Even a small upright can weigh 136 kg (300 lb), and the Steinway concert grand (Model D) weighs 480 kg (1,060 lb). The largest piano available on the general market, the Fazioli F308, weighs 570 kg (1,260 lb).
 

The pinblock, which holds the tuning pins in place, is another area where toughness is important. It is made of hardwood (typically hard maple or beech), and is laminated for strength, stability and longevity. Piano strings (also called piano wire), which must endure years of extreme tension and hard blows, are made of high carbon steel. They are manufactured to vary as little as possible in diameter, since all deviations from uniformity introduce tonal distortion. The bass strings of a piano are made of a steel core wrapped with copper wire, to increase their mass whilst retaining flexibility. If all strings throughout the piano's compass were individual (monochord), the massive bass strings would overpower the upper ranges. Makers compensate for this with the use of double (bichord) strings in the tenor and triple (trichord) strings throughout the treble.
 

The plate (harp), or metal frame, of a piano is usually made of cast iron. A massive plate is advantageous. Since the strings vibrate from the plate at both ends, an insufficiently massive plate would absorb too much of the vibrational energy that should go through the bridge to the soundboard. While some manufacturers use cast steel in their plates, most prefer cast iron. Cast iron is easy to cast and machine, has flexibility sufficient for piano use, is much more resistant to deformation than steel, and is especially tolerant of compression. Plate casting is an art, since dimensions are crucial and the iron shrinks about one percent during cooling. Including an extremely large piece of metal in a piano is potentially an aesthetic handicap. Piano makers overcome this by polishing, painting, and decorating the plate. Plates often include the manufacturer's ornamental medallion. In an effort to make pianos lighter, Alcoa worked with Winter and Company piano manufacturers to make pianos using an aluminum plate during the 1940s. Aluminum piano plates were not widely accepted, and were discontinued.
 

The numerous parts of a piano action are generally made from hardwood, such as maple, beech, and hornbeam, however, since World War II, makers have also incorporated plastics. Early plastics used in some pianos in the late 1940s and 1950s, proved disastrous when they lost strength after a few decades of use. Beginning in 1961, the New York branch of the Steinway firm incorporated Teflon, a synthetic material developed by DuPont, for some parts of its Permafree grand action in place of cloth bushings, but abandoned the experiment in 1982 due to excessive friction and a "clicking" that developed over time; Teflon is "humidity stable" whereas the wood adjacent to the Teflon swells and shrinks with humidity changes, causing problems. More recently, the Kawai firm built pianos with action parts made of more modern materials such as carbon fiber reinforced plastic, and the piano parts manufacturer Wessell, Nickel and Gross has launched a new line of carefully engineered composite parts. Thus far these parts have performed reasonably, but it will take decades to know if they equal the longevity of wood.

In all but the lowest quality pianos the soundboard is made of solid spruce (that is, spruce boards glued together along the side grain). Spruce's high ratio of strength to weight minimizes acoustic impedance while offering strength sufficient to withstand the downward force of the strings. The best piano makers use quarter-sawn, defect-free spruce of close annular grain, carefully seasoning it over a long period before fabricating the soundboards. This is the identical material that is used in quality acoustic guitar soundboards. Cheap pianos often have plywood soundboards.
 

The design of the piano hammers requires having the hammer felt be soft enough so that it will not create loud, very high harmonics that a hard hammer will cause. The hammer must be lightweight enough to move swiftly when a key is pressed; yet at the same time, it must be strong enough so that it can hit strings hard when the player strikes the keys forcefully for fortissimo playing or sforzando accents.
 

In the early years of piano construction, keys were commonly made from sugar pine. In the 2010s, they are usually made of spruce or basswood. Spruce is typically used in high-quality pianos. Black keys were traditionally made of ebony, and the white keys were covered with strips of ivory. However, since ivory-yielding species are now endangered and protected by treaty, or are illegal in some countries, makers use plastics almost exclusively. Also, ivory tends to chip more easily than plastic. Legal ivory can still be obtained in limited quantities. The Yamaha firm invented a plastic called Ivorite that they claim mimics the look and feel of ivory. It has since been imitated by other makers.
 

Almost every modern piano has 52 white keys and 36 black keys for a total of 88 keys (seven octaves plus a minor third, from A₀ to C₈). Many older pianos only have 85 keys (seven octaves from A₀ to A₇). Some piano manufacturers have extended the range further in one or both directions. For example, the Imperial Bösendorfer has nine extra keys at the bass end, giving a total of 97 keys and an eight octave range. These extra keys are sometimes hidden under a small hinged lid that can cover the keys to prevent visual disorientation for pianists unfamiliar with the extra keys, or the colours of the extra white keys are reversed (black instead of white). More recently, manufacturer Stuart & Sons created a piano with 102 keys, going from C₀ to F₈. The extra keys are the same as the other keys in appearance.
 

The extra keys are added primarily for increased resonance from the associated strings; that is, they vibrate sympathetically with other strings whenever the damper pedal is depressed and thus give a fuller tone. Only a very small number of works composed for piano actually use these notes.
 

The toy piano manufacturer Schoenhut started manufacturing both grands and uprights with only 44 or 49 keys, and shorter distance between the keyboard and the pedals. These pianos are true pianos with action and strings. The pianos were introduced to their product line in response to numerous requests in favor of it.
 

There is a rare variant of piano that has double keyboards called the Emánuel Moór Pianoforte. It was invented by Hungarian composer and pianist, Emánuel Moór (19 February 1863 – 20 October 1931). It consisted of two keyboards lying one above each other. The lower keyboard has the usual 88 keys and the upper keyboard has 76 keys. When pressing the upper keyboard the internal mechanism pulls down the corresponding key on the lower keyboard, but an octave higher. This lets a pianist reach two octaves with one hand, impossible on a conventional piano. Due to its double keyboard musical work that were originally created for double-manual harpsichord such as Goldberg Variations by Bach become much easier to play, since playing on a conventional single keyboard piano involve complex and hand-tangling cross-hand movements. The design also featured a special fourth pedal that coupled the lower and upper keyboard, so when playing on the lower keyboard the note one octave higher also played. Only about 60 Emánuel Moór Pianoforte were made, mostly manufactured by Bösendorfer. Other piano manufactures such as Bechstein, Chickering, and Steinway & Sons had also manufactured a few.
 

Pianos have been built with alternative keyboard systems, e.g., the Jankó keyboard.

Pianos have had pedals, or some close equivalent, since the earliest days. (In the 18th century, some pianos used levers pressed upward by the player's knee instead of pedals.) Most grand pianos in the US have three pedals: the soft pedal (una corda), sostenuto, and sustain pedal (from left to right, respectively), while in Europe, the standard is two pedals: the soft pedal and the sustain pedal. Most modern upright pianos also have three pedals: soft pedal, practice pedal and sustain pedal, though older or cheaper models may lack the practice pedal. In Europe the standard for upright pianos is two pedals: the soft and the sustain pedals.
 

The sustain pedal (or, damper pedal) is often simply called "the pedal", since it is the most frequently used. It is placed as the rightmost pedal in the group. It lifts the dampers from all keys, sustaining all played notes. In addition, it alters the overall tone by allowing all strings, including those not directly played, to reverberate. When all of the other strings on the piano can vibrate, this allows sympathetic vibration of strings that are harmonically related to the sounded pitches. For example, if the pianist plays the 440 Hz "A" note, the higher octave "A" notes will also sound sympathetically.

The soft pedal or una corda pedal is placed leftmost in the row of pedals. In grand pianos it shifts the entire action/keyboard assembly to the right (a very few instruments have shifted left) so that the hammers hit two of the three strings for each note. In the earliest pianos whose unisons were bichords rather than trichords, the action shifted so that hammers hit a single string, hence the name una corda, or 'one string'. The effect is to soften the note as well as change the tone. In uprights this action is not possible; instead the pedal moves the hammers closer to the strings, allowing the hammers to strike with less kinetic energy. This produces a slightly softer sound, but no change in timbre.
 

On grand pianos, the middle pedal is a sostenuto pedal. This pedal keeps raised any damper already raised at the moment the pedal is depressed. This makes it possible to sustain selected notes (by depressing the sostenuto pedal before those notes are released) while the player's hands are free to play additional notes (which are not sustained). This can be useful for musical passages with low bass pedal points, in which a bass note is sustained while a series of chords changes over top of it, and other otherwise tricky parts. On many upright pianos, the middle pedal is called the "practice" or celeste pedal. This drops a piece of felt between the hammers and strings, greatly muting the sounds. This pedal can be shifted while depressed, into a "locking" position.
 

There are also non-standard variants. On some pianos (grands and verticals), the middle pedal can be a bass sustain pedal: that is, when it is depressed, the dampers lift off the strings only in the bass section. Players use this pedal to sustain a single bass note or chord over many measures, while playing the melody in the treble section. On the Stuart and Sons piano as well as the largest Fazioli piano, there is a fourth pedal to the left of the principal three. This fourth pedal works in the same way as the soft pedal of an upright piano, moving the hammers closer to the strings
 

The rare transposing piano (an example of which was owned by Irving Berlin) has a middle pedal that functions as a clutch that disengages the keyboard from the mechanism, so the player can move the keyboard to the left or right with a lever. This shifts the entire piano action so the pianist can play music written in one key so that it sounds in a different key. Some piano companies have included extra pedals other than the standard two or three. Crown and Schubert Piano Co. produced a four-pedal piano. Fazioli currently offers a fourth pedal that provides a second soft pedal, that works by bringing the keys closer to the strings.
 

Wing and Son of New York offered a five-pedal piano from approximately 1893 through the 1920s. There is no mention of the company past the 1930s. Labeled left to right, the pedals are Mandolin, Orchestra, Expression, Soft, and Forte (Sustain). The Orchestral pedal produced a sound similar to a tremolo feel by bouncing a set of small beads dangling against the strings, enabling the piano to mimic a mandolin, guitar, banjo, zither and harp, thus the name Orchestral. The Mandolin pedal used a similar approach, lowering a set of felt strips with metal rings in between the hammers and the strings (aka rinky-tink effect). This extended the life of the hammers when the Orch pedal was used, a good idea for practicing, and created an echo-like sound that mimicked playing in an orchestral hall.
 

The pedalier piano, or pedal piano, is a rare type of piano that includes a pedalboard so players can user their feet to play bass register notes, as on an organ. There are two types of pedal piano. On one, the pedal board is an integral part of the instrument, using the same strings and mechanism as the manual keyboard. The other, rarer type, consists of two independent pianos (each with separate mechanics and strings) placed one above the other—one for the hands and one for the feet. This was developed primarily as a practice instrument for organists, though there is a small repertoire written specifically for the instrument.
 

When the key is struck, a chain reaction occurs to produce the sound. First, the key raises the "wippen" mechanism, which forces the jack against the hammer roller (or knuckle). The hammer roller then lifts the lever carrying the hammer. The key also raises the damper; and immediately after the hammer strikes the wire it falls back, allowing the wire to resonate and thus produce sound. When the key is released the damper falls back onto the strings, stopping the wire from vibrating, and thus stopping the sound. The vibrating piano strings themselves are not very loud, but their vibrations are transmitted to a large soundboard that moves air and thus converts the energy to sound. The irregular shape and off-center placement of the bridge ensure that the soundboard vibrates strongly at all frequencies. (See Piano action for a diagram and detailed description of piano parts.) The piano hammer is "thrown" against the strings. This means that once a pianist has pressed or struck a key, and the hammer is set in motion towards the strings, the pressure on the key no longer leads to the player controlling the hammer. Of course, the damper keeps the note sounding until the key is released (or the sustain pedal).
 

There are three factors that influence the pitch of a vibrating wire.

• Length: All other factors the same, the shorter the wire, the higher the pitch.
• Mass per unit length: All other factors the same, the thinner the wire, the higher the pitch.
• Tension: All other factors the same, the tighter the wire, the higher the pitch.

A vibrating wire subdivides itself into many parts vibrating at the same time. Each part produces a pitch of its own, called a partial. A vibrating string has one fundamental and a series of partials. The most pure combination of two pitches is when one is double the frequency of the other.
 

For a repeating wave, the velocity v equals the wavelength λ times the frequency f, v = λf

On the piano string, waves reflect from both ends. The superposition of reflecting waves results in a standing wave pattern, but only for wavelengths λ = 2L, L, 2L/3, L/2, ... = 2L/n, where L is the length of the string. Therefore, the only frequencies produced on a single string are f = nv/2L. Timbre is largely determined by the content of these harmonics. Different instruments have different harmonic content for the same pitch. A real string vibrates at harmonics that are not perfect multiples of the fundamental. This results in a little inharmonicity, which gives richness to the tone but causes significant tuning challenges throughout the compass of the instrument.^[38]
 

Striking the piano key with greater velocity increases the amplitude of the waves and therefore the volume. From pianissimo (pp) to fortissimo (ff) the hammer velocity changes by almost a factor of a hundred. The hammer contact time with the string shortens from 4 milliseconds at pp to less than 2 ms at ff. If two wires adjusted to the same pitch are struck at the same time, the sound produced by one reinforces the other, and a louder combined sound of shorter duration is produced. If one wire vibrates out of synchronization with the other, they subtract from each other and produce a softer tone of longer duration.
 

Pianos are heavy and powerful, yet delicate instruments. Over the years, professional piano movers have developed special techniques for transporting both grands and uprights, which prevent damage to the case and to the piano's mechanical elements. Pianos need regular tuning to keep them on correct pitch. The hammers of pianos are voiced to compensate for gradual hardening of the felt, and other parts also need periodic regulation. Pianos need regular maintenance to ensure the felt hammers and key mechanisms are functioning properly. Aged and worn pianos can be rebuilt or reconditioned by piano rebuilders. Strings eventually need to be replaced. Often, by replacing a great number of their parts, and adjusting them, old instruments can perform as well as new pianos.
 

Piano tuning involves adjusting the tensions of the piano's strings with a specialized wrench, thereby aligning the intervals among their tones so that the instrument is in tune. While guitar and violin players tune their own instruments, pianists usually hire a piano tuner, a specialized technician, to tune their pianos. The piano tuner uses special tools. The meaning of the term in tune in the context of piano tuning is not simply a particular fixed set of pitches. Fine piano tuning carefully assesses the interaction among all notes of the chromatic scale, different for every piano, and thus requires slightly different pitches from any theoretical standard. Pianos are usually tuned to a modified version of the system called equal temperament (see Piano key frequencies for the theoretical piano tuning). In all systems of tuning, each pitch is derived from its relationship to a chosen fixed pitch, usually the internationally recognized standard concert pitch of A₄ (the A above middle C). The term A440 refers to a widely accepted frequency of this pitch – 440 Hz

The relationship between two pitches, called an interval, is the ratio of their absolute frequencies. Two different intervals are perceived as the same when the pairs of pitches involved share the same frequency ratio. The easiest intervals to identify, and the easiest intervals to tune, are those that are just, meaning they have a simple whole-number ratio. The term temperament refers to a tuning system that tempers the just intervals (usually the perfect fifth, which has the ratio 3:2) to satisfy another mathematical property; in equal temperament, a fifth is tempered by narrowing it slightly, achieved by flattening its upper pitch slightly, or raising its lower pitch slightly. A temperament system is also known as a set of "bearings". Tempering an interval causes it to beat, which is a fluctuation in perceived sound intensity due to interference between close (but unequal) pitches. The rate of beating is equal to the frequency differences of any harmonics that are present for both pitches and that coincide or nearly coincide. Piano tuners have to use their ear to "stretch" the tuning of a piano to make it sound in tune. This involves tuning the highest-pitched strings slightly higher and the lowest-pitched strings slightly lower than what a mathematical frequency table (in which octaves are derived by doubling the frequency) would suggest.
 

As with any other musical instrument, the piano may be played from written music, by ear, or through improvisation. Piano technique evolved during the transition from harpsichord and clavichord to fortepiano playing, and continued through the development of the modern piano. Changes in musical styles and audience preferences over the 19th and 20th century, as well as the emergence of virtuoso performers, contributed to this evolution and to the growth of distinct approaches or schools of piano playing. Although technique is often viewed as only the physical execution of a musical idea, many pedagogues and performers stress the interrelatedness of the physical and mental or emotional aspects of piano playing. Well-known approaches to piano technique include those by Dorothy Taubman, Edna Golandsky, Fred Karpoff, Charles-Louis Hanon and Otto Ortmann.
 

Many classical music composers, including Haydn, Mozart, and Beethoven, composed for the fortepiano, a rather different instrument than the modern piano. The fortepiano was a quieter instrument with a narrower dynamic range and a smaller span of octaves. Even composers of the Romantic movement, like Liszt, Chopin, Robert Schumann, Felix Mendelssohn, and Johannes Brahms, wrote for pianos substantially different from 2010-era modern pianos. Contemporary musicians may adjust their interpretation of historical compositions from the 1600s to the 1800s to account for sound quality differences between old and new instruments or to changing performance practice.
 

Starting in Beethoven's later career, the fortepiano evolved into an instrument more like the modern piano of the 2000s. Modern pianos were in wide use by the late 19th century. They featured an octave range larger than the earlier fortepiano instrument, adding around 30 more keys to the instrument, which extended the deep bass range and the high treble range. Factory mass production of upright pianos made them more affordable for a larger number of middle-class people. They appeared in music halls and pubs during the 19th century, providing entertainment through a piano soloist, or in combination with a small dance band. Just as harpsichordists had accompanied singers or dancers performing on stage, or playing for dances, pianists took up this role in the late 1700s and in the following centuries.
 

During the 19th century, American musicians playing for working-class audiences in small pubs and bars, particularly African-Americancomposers, developed new musical genres based on the modern piano. Ragtime music, popularized by composers such as Scott Joplin, reached a broader audience by 1900. The popularity of ragtime music was quickly succeeded by Jazz piano. New techniques and rhythms were invented for the piano, including ostinato for boogie-woogie, and Shearing voicing. George Gershwin's Rhapsody in Blue broke new musical ground by combining American jazz piano with symphonic sounds. Comping, a technique for accompanying jazz vocalists on piano, was exemplified by Duke Ellington's technique. Honky-tonk music, featuring yet another style of piano rhythm, became popular during the same era. Bebop techniques grew out of jazz, with leading composer-pianists such as Thelonious Monk and Bud Powell. In the late 20th century, Bill Evans composed pieces combining classical techniques with his jazz experimentation. In the 1970s, Herbie Hancock was one of the first jazz composer-pianists to find mainstream popularity working with newer urban music techniques such as jazz-funk and jazz-rock.
 

Pianos have also been used prominently in rock and roll and rock music by entertainers such as Jerry Lee Lewis, Little Richard, Keith Emerson (Emerson, Lake & Palmer), Elton John, Ben Folds, Billy Joel, Nicky Hopkins, and Tori Amos, to name a few. Modernist styles of music have also appealed to composers writing for the modern grand piano, including John Cage and Philip Glass.
 

The piano is a crucial instrument in Western classical music, jazz, blues, rock, folk music, and many other Western musical genres. A large number of composers and songwriters are proficient pianists because the piano keyboard offers an effective means of experimenting with complex melodic and harmonic interplay and trying out multiple, independent melody lines that are played at the same time. Pianos are used in film and television scoring, as the large range permits composers to try out melodies and basslines, even if the music will be orchestrated for other instruments. Bandleaders often learn the piano, as it is an excellent instrument upon which to learn new pieces and songs which one will be leading during a performance. The piano is an essential tool in music education in elementary and secondary schools and universities and colleges. Most music classrooms and practice rooms have a piano. Pianos are used to help teach music theory, music history and music appreciation classes. Many conductors are trained in piano, because it allows them to play parts of the symphonies they are conducting (using a piano reduction or doing a reduction from the full score), so that they can develop their interpretation.