The Open Audio License is a free music license, created in 2001 by the Electronic Frontier Foundation (EFF). It provides freedom and openness of use for music and other expressive works. The EFF now encourages artists to use the Creative Commons Attribution-ShareAlike license instead of the Open Audio License, and it "designates the Creative Commons Attribution Share-Alike license as version 2.0 of the Open Audio License." 
Publication of the first version of the Open Audio License spurred the creation of the original Open Music Registry to support the license and provide a directory for finding works released under the license.
The following sites provide content under the Open Audio License: