Common Music
CM is an object-oriented Music composition environment. It produces sound by transforming a high-level representation of musical structure into a variety of control protocols for sound synthesis and display. For more information, see the CM web page on SourceForge or the CM mailing list. Note that CM3 is C++ and Scheme. Common Music 2 is written in Common Lisp and released under the LLGPL.

There is a 2004 e-book out by Heinrich Konrad Taube (creator of CM), called Notes from the Metalevel An Introduction to Computer Composition, about computer music representation and composition using CM (and also includes quite a bit of introductory Lisp). See also: Common Music Functions by Drew Krause: Lisp Functions and Sketchbooks.