Grand piano by Louis Bas of
, France, 1781. Earliest French grand piano known to survive; includes an inverted wrestplank and action derived from the work of Bartolomeo Cristofori (ca. 1700) with ornately decorated soundboard.
Early piano replica by the modern builder Paul McNulty, after Walter & Sohn, 1805
The piano was founded on earlier technological innovations in
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
 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 allows expressive control of volume and sustain, it is too quiet for large performances in big halls. The harpsichord produces a sufficiently loud sound, especially when a coupler joins each key to both manuals of a two-manual harpsichord, but it offers no dynamic or accent-based expressive control over each note. A harpsichord can't produce a variety of dynamic levels from the same keyboard during a musical passage (though a player can use a harpsichord with two manuals to alternate between two different
stops [settings on the harpsichord that determine which set of strings sound], which could include a louder stop and a quieter stop). The piano offers the best of both instruments, combining the ability to play loudly and perform sharp accents. The piano can project more during
piano concertos and play in larger venues, with dynamic control that permits 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.
Cristofori's new instrument remained relatively unknown until an Italian writer,
Scipione Maffei, wrote an enthusiastic article about it in 1711, including a diagram of the mechanism, that was translated into German and widely distributed.
 Most of the next generation of piano builders started their work based on reading the article. One of these builders was
Gottfried Silbermann, better known as an
organ builder. Silbermann's pianos were virtually direct copies of Cristofori's, with one important addition: Silbermann invented the forerunner of the modern
sustain pedal, which lifts all the dampers from the strings simultaneously. This allows the pianist to sustain the notes that they have depressed even after their fingers are no longer pressing down the keys. This innovation enabled pianists to, for example, play a loud chord with both hands in the lower register of the instrument, sustain the chord with the sustain pedal, and then, with the chord continuing to sound, relocate their hands to a different register of the keyboard in preparation for a subsequent section.
Johann Sebastian Bach one of his early instruments in the 1730s, but Bach did not like the instrument at that time, claiming that the higher notes were too soft to allow a full dynamic range. Although this earned him some animosity from Silbermann, the criticism was apparently heeded. Bach did approve of a later instrument he saw in 1747, and even served as an agent in selling Silbermann's pianos. "Instrument: piano et forte genandt"–a reference to the instrument's ability to play soft and loud–was an expression that Bach used to help sell the instrument when he was acting as Silbermann's agent in 1749.
Piano-making flourished during the late 18th century in the
Viennese school, which included
Johann Andreas Stein (who worked in
Augsburg, Germany) and the Viennese makers
Nannette Streicher (daughter of Stein) and
Anton Walter. Viennese-style pianos were built with wood frames, two strings per note, and leather-covered hammers. Some of these Viennese pianos had the opposite coloring of modern-day pianos; the natural keys were black and the accidental keys white.
 It was for such instruments that
Wolfgang Amadeus Mozart composed his
sonatas, and replicas of them are built in the 21st century for use in
authentic-instrument performance of his music. The pianos of Mozart's day had a softer, more ethereal tone than 21st century pianos or English pianos, with less sustaining power. The term
fortepiano now distinguishes these early instruments (and modern re-creations) from later pianos.
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.
Broadwood square action (click for page with legend)
Early technological progress in the late 1700s owed much to the firm of
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.
Erard square action (click for page with legend)
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
 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 crossed the 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.
Duplex scaling of an 1883
Model 'A'. From lower left to upper right: main sounding length of strings, treble bridge, duplex string length, duplex bar (nickel-plated bar parallel to bridge), hitchpins, plate strut with bearing bolt, plate hole.
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),
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.
Variations in shape and design
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 mechanism and strings in upright pianos are perpendicular to the keys.
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.