Unusual Piano Design

Pressing a key on the piano's keyboard causes a felt-covered hammer to strike steel strings. The hammers rebound, allowing the strings to continue vibrating at their resonant frequency. These vibrations are transmitted through a bridge to a sounding board that couples the acoustic energy to the air so that it can be heard as sound. When the key is released, a damper stops the string's vibration. See the article on Piano key frequencies for a picture of the piano keyboard and the location of middle-C. Pianos are percussion instruments. According to the Hornbostel-Sachs method of music classification, they are grouped with chordophones.
The word piano is a shortened form of the word pianoforte, which derives from the original Italian name for the instrument, clavicembalo [or gravicembalo] col piano e forte (literally harpsichord capable of playing at the normal level, or more strongly). The musical terms "piano" and "forte" are usually interpreted as "soft" and "loud", but this is not strictly what they mean in Italian. "Piano" means here a plane or level, suggesting the normal level of playing. "Forte" would mean a stronger, more powerful level of playing, effectively louder than usual.
This refers to the instrument's responsiveness to keyboard touch, which allows the pianist to produce notes at different dynamic levels by controlling the speed with which the hammers hit the strings.