Pressing a key on the piano's keyboard causes a padded (often with felt) hammer to strike steelstrings. The hammers rebound, and the strings continue to vibrate at their resonant frequency. These vibrations are transmitted through a bridge to a sounding board that more efficiently couples the acoustic energy to the air. The sound would otherwise be no louder than that directly produced by the strings. When the key is released, a damper stops the string's vibration and the sound. In the Hornbostel-Sachs system of instrument classification, pianos are considered chordophones.
The word piano is a shortened form of pianoforte (PF), the Italian word for the instrument (which in turn derives from the previous terms gravicembalo col piano e forte and fortepiano). The Italian musical terms piano and forte indicate "soft" and "strong" respectively, in this context referring to the variations in sound volume the instrument produces in response to a pianist's touch on the keys: the greater the velocity of a key press, the greater the force of the hammer hitting the strings, and the louder the sound of the note produced. This is in contrast to the predecessor of the piano, the harpsichord, which cannot produce different dynamics depending on how hard the key is pressed.
Fortepiano by Paul McNulty after Walter & Sohn, ca. 1805
Fortepiano designates the early version of the piano, from its invention by the Italian instrument maker Bartolomeo Cristofori around 1700 up to the early 19th century. It was the instrument for which Haydn, Mozart, and the early Beethoven wrote their piano music. Starting in Beethoven's time, the fortepiano began a period of steady evolution, culminating in the late 19th century with the modern grand. The earlier fortepiano became obsolete and was absent from the musical scene for many decades. In the 20th century the fortepiano was revived, following the rise of interest in historically informed performance.
Bösendorfer (L. Bösendorfer Klavierfabrik GmbH) is an Austrian piano manufacturer, now a wholly owned subsidiary of Yamaha. The brand is known for producing pianos with a uniquely rich, singing, and sustaining tone. Bösendorfer is unusual in that it produces 97- and 92-key models in addition to instruments with standard 88-key keyboards. Bösendorfer makes seven models of grand piano (from 5'8" to 9'6") and one vertical piano (52" upright). The 9'6" Imperial Grand is one of the world's largest pianos.