Recent Developments in Computer Sound Analysis and Synthesis

Abstract

Some 40 years after the birth of computer music technology, new developments have emerged from research institutions that have gradually come into public use. This article examines recent developments that have offered new possibilities in sound analysis and synthesis. While they are typically issued from laboratories, these possibilities have reached not only professionals, but also a large public that is making or simply listening to music. First, we examine additive synthesis, one of the oldest methods of making computer music. Additive synthesis is the summation of time-varying sinusoidal components. Its development and use have been discouraged by several drawbacks, including computation cost, difficulty of introducing precisely controlled noisy components, and the challenge of controlling hundreds of sinusoids. Methods have been designed however to automatically analyze sounds in terms of partials and noise that can then be applied directly to additive synthesis (Serra 1989; Rodet and Depalle 1992), and we have produced a new additive synthesis method named FFT-1 that is based on spectral envelopes and the inverse Fast Fourier Transform. We will explain how this method decreases the computation cost and renders the control more simple, direct, and user-friendly. Commercial applications should appear this year for professional users and soon after for the public (Oberheim 1994). After the additive technique, we will examine the new possibilities offered by processing natural sound and voice. The recreation of a castrato voice by the means of sound processing (Depalle, Garcia and Rodet 1994) has been done to produce the soundtrack for a film and a CD about Carlo Farinelli (or Carlo Broschi), the famous castrato of the 18th century. This example is particularly interesting for several reasons. First, it is extremely difficult to synthesize a high-quality singing voice for a concert or a CD (Bennett and Rodet 1989). Second, the producers were able to create 40 minutes of a new castrato-like singing voice in a limited amount of time. Third, this is the first application of a technique that is analogous to morphing. And finally, the CD and the film have reached millions of