In an acoustic piano, a weighted felt pad that rests on each set of strings to stop them from vibrating. The damper raises when a key is struck, allowing that note’s strings to vibrate and decay until the key is released, causing the damper to fall back into its “down” position. Alternately, the dampers are raised when either the sustain or sostenuto pedals are pressed; each permits a particular set of sympathetic vibrations from the other piano strings to sound.
Electro-acoustic pianos and other mechanical keyboards also used dampers. The Fender Rhodes piano (in which the strings are replaced by a series of tines and tonebars) employed a fairly traditional set of dampers. The Wurlitzer Electric piano used a variation of the same, as did some versions of the Hohner Clavinet. One unique instrument, the Hohner Pianet, used its dampers to “strike” the notes as well as damp them. Its foam dampers, which rested on top of tines (which were similar to a Wurlitzer’s), had adhesive tape mounted to the bottom, which stuck to the tines. When the key was struck, the adhesive “pulled” the tine upward until the resistance of the metal was too great; the tine then “snapped” back down, setting it into vibration.