An optional middle pedal provided on some pianos that enables the performer to sustain the sound of a note held down at the moment the pedal is depressed. The principle of selective sustaining was addressed by Jean Louis Boisselot in a mechanism exhibited at the Paris Exposition of 1844. Boisselot's ideas were subsequently taken up by Claude Montal, who exhibited his pédale de prolongement at the London International Exhibition of 1862. Other inventions designed to achieve the same effect were developed by Lentz of Paris and Zachariae of Stuttgart. The modern sostenuto pedal, however, owes most to Steinway's mechanism, patented in 1874. The sostenuto pedal should not be confused with the Sustaining pedal, the normal ‘loud’ or ‘damper’ pedal that removes the dampers from all the strings of the instrument.
EDWIN M. RIPIN/DAVID ROWLAND