Analysis and synthesis of the singing voice and mnsical applications

Abstract

IRCAM (Institut de Recherche et de Coordination Acoustique/Musique) has been involved in sound analysis and synthesis for contemporary music creation for many years. Accurate analysis and high‐quality sound synthesis are thus extensively studied. Some of the methods that have been developed are described with particular attention to the singing voice and speech. A power spectral density estimate has been developed of the speech signal, which is simultaneously very precise and computed on very short segments of the signal in order to follow rapid transitions such as those found in plosives. Spectral envelopes are represented in a flexible way: They are coded in terms of frequency, amplitude, and bandwidth of pairs of conjugate poles (formants). An algorithm has been developed giving an harmonic/noisy decision in narrow frequency bands covering the entire spectrum. This technique has greatly improved the sound quality. Several synthesis methods have been developed and compared, including formant waveform synthesis (analogous to parallel formant synthesis), additive synthesis, and serial filter synthesis. Two types of synthesis rules have been studied. On the one hand, rules concerning phoneme coarticulation using formant coded diphones, sophisticated algorithm smoothing formant trajectories by taking into account three successive phonemes, durations of phonemes, speed of singing, speed of transitions, and relative timing of formant trajectories. On the other hand, a set of rules has been built with musical performance. Those rules calculate such features as vibrato excursion and rate, vocal effort, and formant locations according to fundamental frequency. Examples of synthesis by rule are given showing different types of voices and styles plus excerpts from concert pieces.