a control circuit for shaded - pole motors used in an acoustic pulsato system for producing special musical effects . the system includes a horn - type loudspeaker connected to a shaded - pole motor and / or a drum - type loudspeaker connected to a shaded - pole motor . each type of loudspeaker has a feedback circuit and a means for the operator to select the desired speed for the motor . the feedback circuit quickly adjusts the actual speed of the motor to correspond to the selected speed by controlling the amount of current or power supplied to the motor . the drum - type loudspeaker feedback circuit also includes a braking circuit to quickly stop the motor and the drum rotation to prevent unpleasant spurious signals which occur if the drum loudspeaker is permitted to coast to a stop on a slower speed .