The Arts Libraries includes some extensive and amazing audio databases. Not just music, but speeches, poetry and much more can be found.
For over 52,000 audio tracks of classical music from the Medieval to the contemporary, with chamber music, symphonies, choral music, solo vocal and instrumental, and other forms, go to The Classical Music Library
Smithsonian Global Sound has audio tracks and related texts documenting the world’s musical traditions, along with spoken word recordings such as political speeches, and even nature sounds. The music ranges from remote cultures worldwide to famous folk musicians. Over 35,000 tracks are available!
The Database of Recorded American Music contains a wide spectrum of North American (USA) music, from 19th century to contemporary compositions, electronic music, folk, jazz, Native American music, opera and musical theater.