JPS6488598A - Acoustic signal formation circuit - Google Patents

Abstract

PURPOSE: To output both of a chime sound and a tremolo by switching and to reduce the number of parts to reduce the cost by adding a switching circuit or the like which switches a one shot trigger circuit to an oscillation circuit. CONSTITUTION: A multi-circuit is used which can perform switching between the one shot mode and the oscillation mode, where a frequency which is lower than an audible frequency but has a relatively short period is oscillated, in accordance with a second control signal. In the one shot mode, the rise of a first control signal is used as a trigger to generate a pulse having relatively long time width, and amplitude-modulated waves of the signal, which is obtained by differentiating this pulse by a differential circuit having a relatively long period, and an audible frequency signal are obtained; and in the oscillation mode, a square wave signal having a period shorter than that in the one shot mode is generated, and amplitude-modulated waves of this signal and the audible frequency signal are obtained. Consequently, the multi-circuit is operated as a chime sound generation circuit in the one shot mode and is operated as a tremolo generation circuit in the oscillation mode. Thus, the chime sound and the tremolo can be outputted from one circuit by switching, and the circuit is simplified, and the number of parts and the cost are reduced.