Control for turning one or more ranks of pipes, piano, percussion instruments such as xylophones and bells, or other effects on and off in an organ or automatic instrument. * Synonyms: stop, organ stop.

The threaded pin that protrudes from the end cap of a musical box cylinder and rests against the snail cam. Turning the pin allows for fine adjustment of the cylinder position in order to align the registration marks with the tips of the comb teeth.

The selection of stops to be used while playing a pipe organ.

The screw located in the rear of the governor block which allows for the depthing adjustment of the endless screw with the second wheel by sliding the potence in and out.

Spring-loaded bellows connected to the main pressure or suction supply in a pneumatic instrument, with an escape valve or a choker, which helps to keep the air pressure or suction at a constant level. * Synonym: equalizer.