SuperCollider is an environment and programming language for real time
audio synthesis and algorithmic composition. It provides an
interpreted object-oriented language which functions as a network
client to a state of the art, realtime sound synthesis server.

SuperCollider was written by James McCartney over a period of many
years, and is now an open source (GPL) project maintained and
developed by various people. It is used by musicians, scientists, and
artists working with sound. For some background, see SuperCollider
described by Wikipedia.