The POD System of Interactive Composition Programs
Barry Truax · Computer Music Journal · 1977
The POD system consists of a number of programs for real-time synthesis and interactive composition established by the present author at the Institute of Sonology, Utrecht (1972-73), [11 and Simon Fraser University, Vancouver (1973-present). [2] Related versions of the programs exist at other centers in Canada, and Europe. All run on minicomputers of various types (PDP-I 5, HP 2116, PDP-1 1, Nova 3) and are accessible to users with little computer experience. The basic level of the programs utilizes realtime monophonic synthesis (either fixed wave-form synthesis with amplitude modulation, or the frequency modulation method developed by John Chowning at Stanford), [3] whereas a higher program level calculates non-real-time pressure functions which can be mixed and output at high sampling rates. The compositional model embodied in the POD system can be represented in a block diagram such as that of Fig. 1. The user strategy, external to the program, works with the mental representation that the user has of a possible goal structure, and that of the present structure derived from hearing the sound synthesis result; this feedback is shown by the dashed line in Fig. 1. The interactive nature of the program lies in the user exercising control over various parts of the program to obtain successive modifications of the synthesized structure. That is, the user works on both the sonic and syntactic levels within the program, the