Digital sound synthesizing device using a closed wave guide network with

Abstract

In a device which excites an oscillating signal in a closed loop containing a delay circuit and a filter so as to synthesize a sound of pitch corresponding to the total delay time in the closed loop, arithmetic operations are performed in the closed loop, in response to a change in a color controlling coefficient caused during generation of the sound, for interpolating delayed output signals from plural points in the loop having different delay time. This interpolation compensates for a variation in the signal delay time in the closed loop resultant from the change in the filter coefficient, to allow the entire closed loop to provide such a total delay time that excites oscillation corresponding to a desired pitch. The closed loop also includes first and second filters. When generation of the sound is to be started, the delay time adjustment or pitch modification is performed by using, as the first filter, an all-pass filter that has the advantage of having no adverse effect on the frequency characteristic of sound. During generation of the sound, so as to avoid the adverse effect resultant from a variation in the coefficient of the all-pass filter, variable control of the delay time or variation control of the pitch is performed by using, as the second filter, a low-pass filter that functions as a delay interpolator.