PURPOSE: To vary a variable of the singing apparatus, and to simplify and miniaturize a sound volume control circuit by varying the pulse width of a pulse control signal to a transistor.

CONSTITUTION: By a control signal (a), a transistor Q0 is controlled. The control signal (a) makes a voltage constant and varies pulse width to three steps of control signals a1-a3. Electric power applied to a sounder S of a load is determined by a current-flow angle of the control transistor Q0. Accordingly, in a sounding body for utilizing the resonance of a sounder, etc., by fixing an applied voltage and varying the pulse width, energy to be applied can be varied. Also, the sounder S is constituted of an inductance and an equivalent resistance of a diaphragm, and energy to be applied is expressed by (voltage)×(current), therefore the energy can be expressed nearly by the current-flow angle based on transient current and voltage characteristics. A pitch (frequency) of a sound is controlled by varying the repeat frequency of the control signal (a).