Sustaining pedal [damper pedal, loud pedal, open pedal].

A name often used for the right pedal of the piano, which when depressed raises the dampers from all the strings, allowing them to vibrate freely in sympathy with any notes being played. In earlier pianos, this effect was sometimes achieved by the use of knee-levers or hand-stops. It was sometimes possible to raise the treble and bass dampers separately, as on those instruments provided with a divided pedal or the less common ones with two damper pedals.

EDWIN M. RIPIN