The large cast-iron, round-leather belted pulley is connected to the motor. This, pulley in turn drives the pump crankshaft via roller chain reduction gears, providing a powerful, slow and steady speed for the bellows type feeder pump.

The feeder pump, fastened to the floor of the PianOrchestra, serves a dual purpose, and provides both vacuum (front set of bellows) and wind-pressure (rear set of bellows, which are not visible).