Musopen is a non-profit focused on increasing access to music by providing recordings to the public for free, without copyright restrictions. Search by composer, musician, time period, or genre. Click on any item to listen, download, and view copyright license:
The Free Music Archive is an interactive library of high-quality, legal audio downloads. You can browse works by creator or genre, and each item includes a clearly identified Creative Commons license as well as a link to contact the creator.
The University of Houston's Digital History website contains a collection of historical music that is in the public domain (available for your use without permission from copyright holders). The collection is organized loosely into genres or time periods, including 1920s, Blues, Civil War, Irish, Jazz, Patriotic, WWI, and others.