Nyquist is a programming language for sound synthesis and analysis based on the Lisp programming language. It is an extension of the XLISP dialect of Lisp.
The Nyquist programming language and interpreter were written by Roger Dannenberg (co-founder of Audacity) at Carnegie Mellon University, with support from Yamaha Corporation and IBM.
Nyquist was contemporary with the birth of Audacity and is essentially Audacity’s own user-customisable plug-in format.
Detailed technical information about Nyquist programming and plugins together with links to downloadable Nyquist plugins can be found in the manual: Nyquist.