A Tutorial on Digital Sound Synthesis Techniques

Progress in electronics and computer technology has led to an ever-increasing utilization of digital techniques for musical sound production. Some of these are the digital equivalents of techniques employed in analog synthesizers and in other fields of electrical engineering. Other techniques have been specifically developed for digital music devices and are peculiar to these. This paper introduces the fundamentals of the main digital synthesis techniques. Mathematical developments have been restricted in the exposition and can be found in the papers listed in the references. To simplify the discussion, whenever possible, the techniques are presented with reference to continuous signals. Sound synthesis is a procedure used to produce a sound without the help of acoustic instruments. In digital synthesis, a sound is represented by a sequence of numbers (samples). Hence, a digital synthesis technique consists of a computing procedure or mathematical formula, which computes each sample value. Normally, the synthesis formula depends on some values, that is, parameters. Frequency and amplitude are examples of such parameters. Parameters can be constant or slowly time variant during the sound. Time-variant parameters are also called control functions. Synthesis techniques can be classified as (1) generation techniques (Fig. la), which directly produce the signal from given data, and (2) transformation techniques (Fig. Ib), which can be divided into two stages, the generation of one or more simple signals and their modification. Often, more or less elaborate combinations of these techniques are employed. Fixed-Waveform Synthesis