A piano (French: piano, German: Klavier, Russian: фортепиано, Spanish: piano) (short for pianoforte, which is Italian for "soft - loud") is a stringed musical instrument played by means of a mechanical linkage to a keyboard. Pressing the keys down causes hammers to strike the strings. It was referred to by famous composer Ludwig van Beethoven as "the god of all instruments". Franz Liszt famously stated, "Why do you need an orchestra when you have a grand piano with 88 keys?"
A modern piano typically has three pedals. The left pedal is called the soft pedal or una corda. On a grand piano it shifts the hammer assembly so that the hammers strike only two of the three strings for each note (or, in the case of the double-strung notes, only one of the two strings). This does not just make the sound softer, it changes its tonal characteristics.
The right pedal is the "loud pedal" or "damper pedal." Normally, releasing a key causes a felt damper to press against the string so that it stops sounding. The damper pedal prevents the dampers from actuating, so that every note continues to sound until the sound decays naturally. The middle pedal is the "sustaining pedal." It affects only the dampers that are lifted when the pedal is engaged. The result is that the pianist can strike a chord, and engage the sustaining pedal; the chord will then continue to sound while freeing the pianist hand's to play other notes.
Smaller piano models may take shortcuts with the pedal functions. The "soft pedal" may move the hammers closer to the strings instead of shifting them sideways. The "sustaining pedal" may simply disengage the dampers from all of the bass strings, or may be missing altogether. On some upright models, the middle pedal places a large sheet of felt over the entire set of strings, acting to dampen the sound considerably.
On Fazioli concert grand pianos, there is a fourth pedal which moves the hammers closer or farther away from the strings, giving an entirely different sound than the una corda pedal.
In 1700 a keyboard player was faced with harpsichord or one of its siblings, which had brilliant sound but little dynamic modulation, and even fewer expressive qualities; or the clavichord on which one could control the dynamics through touch, but only softly, and with little chance of being heard within an ensemble. (There was the dulcimer, but it had no keyboard.) Starting from around this date when an Italian, one Bartolemeo Cristofori, began experimenting with “a harpsichord with loud and soft”, to the first decades of the 19th century when the piano reached its more or less modern form, the development of the piano went ahead in Germany and Austria, France, England and America – developments in the mechanics of the action, on the shape and strength of the box, the introduction finally in America of the single-cast immensely strong metal frame, improvements in the pedal action; all helped the formation of an instrument that was to be as suitable for the family parlour as in the concert hall.
By the 1770s the piano, in a stage of development we now often refer to as the “forte-piano” had taken over from the harpsichord as the instrument of choice for the composers of the day: the Bach sons, Joseph Haydn, Mozart and others. In another 40 to 50 years its power and expressive range had reached relatively modern standards. (Perhaps the best way to illustrate this is to listen to a piano sonata written by Haydn or Mozart, then compare it to nearly any of the later Beethoven sonatas – he wrote 32, and their emotional range and expressive power are positively symphonic!)
There are very few great or well-known composers, writing since 1800, who do not have a sizable corpus of piano music amongst their works. As well as Beethoven, the 19th century gave us Schubert, Mendelssohn, Schumann, Chopin, Liszt, Brahms; all of which are in the top row of that pantheon of western music, and all of which, if they had written nothing but music featuring the piano (like Chopin) would still be household names today. This would continue into the 20th century with Debussy, Ravel, Poulenc, Rachmaninov, Messiaen and others making important piano contributions. Many of these composers were fine pianists themselves – Liszt and Chopin of course, Brahms (who was offered a concert tour of America when he was only ten, and took up composing against the advice of all those around him. Brahms wrote 4-hand piano versions of all his major works and spruiked them at his concerts, much the same as the “latest CD” is sold in the foyer at a concert or recital today.) Rachmaninov never did work out whether he wanted to play, conduct or write. The young Dmitri Shostakovich kept himself going by playing “accompaniment” in silent movie houses. Even composers not known for their piano compositions have been concert-class pianists- - Benjamin Britten and Leonard Bernstein are examples.
In the 18th century, the piano replaced the clavichord as the instrument of composition, a position it still holds.