The piano, the common abbreviation of pianoforte, is a stringed musical instrument in which the strings are struck by felt-covered hammers controlled by a keyboard. It has been the most popular keyboard instrument for almost two centuries. Classified technically as a board zither--an instrument in which strings are passed over a board that functions as a resonator--the piano belongs to the dulcimer (struck zither) family, in contradistinction to the harpsichord, played by plucking the strings, and the clavichord, in which the strings are touched by tangents.
Pianos have been built in three basic forms: the obsolete rectangular or square, the upright, and the wing-shaped grand. The latter has been preferred generally for concert performance, whereas the various square, and later the upright, forms have been the favorite instruments for the home.
The standard range of the modern piano is 7(1)/(3) octaves, requiring 88 keys. Behind the keyboard lies the pinblock, made of laminated hardwood and drilled to receive the tuning pins. Between the pinblock and the soundboard, which extends over most of the inside area of the instrument, a small gap is left through which the hammers rise to strike the strings. A hardwood bridge glued to the soundboard transmits the vibrations excited in the string by the hammer blow to the soundboard, which in its vibration amplifies and enriches the sound. A massive cast metal frame is set over the pinblock and soundboard. The tuning pins protrude through the front end of the frame, and the far end bears the hitchpins to which the other ends of the strings are attached; thus the metal frame sustains the enormous tension of the strings. The instrument has two strings per note in the middle range and three strings per note in the treble range. The "action," a mechanism attached to the keyboard, converts the downward pressure on the key into a hammer stroke, allowing for an "escapement," or release, of the hammer after it has struck the string. Dampers placed above the strings stop the strings from vibrating--thus stopping the sound--immediately on release of the key. Most modern pianos have three pedals, although the middle pedal is sometimes omitted. The left, or "soft," pedal shifts the keyboard and the action to the right, causing the hammers in the middle and treble range to strike one less string each. The middle, or sostenuto, pedal holds in a raised position dampers for keys that have been struck and held prior to the activation of the pedal. The right pedal raises all the dampers, allowing the strings to vibrate freely.
In the first decade of the 18th century the Italian Bartolommeo Cristofori (1655-1731) succeeded in installing an efficient hammer action into the case of a harpsichord, naming his invention gravicembalo col piano e forte ("harpsichord with soft and loud") for the new instrument's ability to vary the loudness of its tone according to the force of the player's finger stroke, which is not possible on the harpsichord.
Johann Andreas Stein perfected the so-called Viennese action, in which the hammer is pried or snapped up against the string; it was inexpensive to produce, reliable, and extremely sensitive to the touch. This action, together with the lightly constructed case of the Viennese piano, yielded an ideal instrument for the mature keyboard works of Haydn, Mozart, and their contemporaries.
About 1760, Johannes Zumpe immigrated to England with a group of German piano makers, there introducing the primitive single action in which the hammer is tossed up against the string by a jack attached to the key. In its developed form this action became known as the English action. The powerful strokes possible with this action together with the heavier stringing and framing of the late-18th-century English piano resulted in an instrument with greater volume of sound and sustaining power than the Viennese piano. Efforts to combine the power and cantabile (singing quality) of the English instrument with the responsiveness and stability of the Viennese piano resulted in the repetition action patented (1821) by the French maker Sebastien Erard. Additional efforts resulted in an ever-increasing reinforcement of the case--first with heavier wood framing and later through the introduction of metal braces, culminating in the complete cast-iron frame patented (1825) by the American piano builder Alpheus Babcock.
Most of the composers of the last two centuries have been pianists. Muzio Clementi was among the first to exploit an idiomatic and frankly virtuosic approach to the piano in contrast to the keyboard style of Haydn and Mozart, which evolved gradually out of the traditions of the harpsichord and clavichord. For a brief period in the early 19th century the possibilities of the piano as a serious musical instrument were obscured by its bravura (technical display) aspect; consequently, the mature keyboard works of Beethoven and Schubert were largely ignored by the public in favor of countless virtuosic pieces de concert by a host of pianist-composers. It remained for the great romantic composers for the keyboard, led by Frederic Chopin and Franz Liszt, to reconcile the bravura style with the highest musical ends.
The 19th century, with its cult of the virtuoso and its favoring of piano ownership as a cultural status symbol, was truly the golden age of the instrument. In the 20th century the piano's dominance in concert music has been diminished by a stylistic evolution away from the cantabile, the personalistic, and the virtuosic.