The phase vocoder is a tool used to perform time-stretching and pitch-shifting on recorded sounds. Its name derives from the early "vocoders" (contraction from "voice encoders"), which used a set of bandpass filters in parallel over many frequency bands, to crudely analyze and reconstruct speech. In this article, Richard Dudas and Cort Lippe explain the workings of a phase-vocoder as well as how to construct and modify one in Max/MSP.
In our last article about the phase vocoder we saw how to create a basic phase vocoder for time-stretching. While it is by no means a simple MSP patch, it is a useful one. In addition to time-stretching, the phase vocoder has been used for transposition and "freeze" effects, which we will be discussing in this article.
Amnon Wolman creates music with technology and for instruments with two distinctive features: first, a subtle and complex relationship with popular culture and second, a concern for the dramatic nature of sonic evolution. His first release on the c74 record label is "Dangerous Bend." In this conversation with Ben Nevile, Wolman discusses his romantic compositional techniques and reveals the unusual nature of his introduction to computer-based music.