Musopen
musopen.org
A nonprofit that records and releases public domain classical music with no performance rights restrictions — providing free sheet music, recordings, and textbooks for composers, educators, and filmmakers.
Why it is useful
Classical music recordings are theoretically in the public domain, but new performances carry their own copyright — which is why most classical music cannot be freely used. Musopen commissions new recordings specifically to release them copyright-free, making them legal for use in films, games, education, and any other project. The sheet music library is also comprehensive and free.