Generation of musical tones in PARCOR speech synthesizer

Abstract

This paper discusses a method in which the impulse response of the digital filter in PARCOR speech synthesizer is used as a musical tone. the following items are discussed. (1) Creation of musical tone-scale by pole frequency of digital filter. (2) the effect of operational accuracy on the quality of a musical tone, which is an important factor in determining the size of the circuit. (3) Improvement of the quality of the musical tone. For the present circuit size where the word length of k-parameters is 10 bits and the operational bit length is 14, the sinusoidal wave above C4 has the sufficiently accurate pitch frequency, and there is no problem in creating the musical tone scale. However, it was seen that the impulse response is attenuated in a short period, and a musical tone with practicable envelope characteristics cannot be obtained. As a method to solve this difficulty, a method is proposed whereby the lower bits are rounded-up in the multiplier output of the filter circuit. the effectiveness of the proposed method has been verified. By this scheme, a PARCOR speech synthesis LSI has been realized which can generate sinusoidal waves of various kinds of envelopes as well as musical tones.