Performing STFT and ISTFT in the microsound synthesis framework of the LC computer music programming language

Abstract

This paper describes how the short-term Fourier transform (STFT) and inverse short-term Fourier transform (ISTFT) are integrated within the sound synthesis framework of LC, a new computer music programming language, which the authors prototyped, and discusses its benefits for computer music programming. In addition to the traditional unit-generator-based sound synthesis framework, LC provides a framework for microsound synthesis, which is highly independent from the unit-generator concept, and STFT and ISTFT can be also performed within the same framework. While the unit-analyzer concept in the ChucK audio programming language shows a certain degree of similarity to LC’s programming model for STFT and ISTFT, in that both languages allow direct access to low-level spectral data from user programs, due to the dependence on the unit-generator-based sound synthesis framework, a ChucK program that utilizes unit analyzers can exhibit unnecessary complexity in its implementation, when the hop sizes differ among the STFT frames in the program. On the other hand, thanks to the high independence from the unit-generator concept, LC’s microsound synthesis framework can provide a simpler and terser programming model and avoid such unnecessary complications. As other unit-generator languages can also exhibit similar problems as seen in ChucK’s unit analyzers, depending on its sound synthesis framework design, such a language design of LC would be beneficial, not just as a design exemplar for next generation computer music languages, but also to reconsider the design of existing unit-generator languages on such issues regarding how STFT should be integrated in a unit-generator language and whether unit-generators should fully synchronize the audio computation with the advance of global system time.