Working Knowledge; January 1999; Scientific American Magazine; by Mohr; 2 Page(s)

The piano dates back to the early 1700s, when a Florentine harpsichord maker named Bartolomeo Cristofori, seeking to improve the expressiveness of the harpsichord, devised the "escapement action"-a mechanism that, in modified form, lies at the heart of all modern pianos. Unlike the harpsichord, which features a plucking mechanism attached directly to a key, the piano has a mechanical interface between each key and a corresponding felt-tipped hammer. This complex system of levers, screws, springs and bearings allows the pianist to play quickly and to produce a wide range of dynamics and nuance.

The lever system magnifies movement so that while the key travels less than half an inch from its rest position, the hammer travels one and three quarters inches to the string above. Just before the hammer strikes the string, the action mechanism must disengage, or "escape," from its contact with the key. The hammer then strikes the string on its own momentum and falls back instantaneously so the string can vibrate freely. Without escapement, the hammer would jam against the string, stifling vibration. Modern pianos have a double escapement action that allows the hammer to be reactivated even when the key has not yet been fully released; thus, a single note can be played in fast repetition.