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.
Blüthner, formally Julius Blüthner Pianofortefabrik GmbH, is a piano-manufacturing company founded by Julius Blüthner in 1853 in Leipzig, Germany. Today Blüthner pianos come in several sizes of grands from 5 ft to 9 ft in size. Innovations such as aliquot stringing and angle-cut hammers create a unique voice for the Blüthner instrument. The special lightweight piano for use on the ZeppelinLZ 129 Hindenburg was also a Blüthner.