Check license on individual pieces... https://www.mutopiaproject.org/ https://www.mutopiaproject.org/ says "all in the Public Domain or under Creative Commons

Check license on individual pieces... https://www.mutopiaproject.org/ https://www.mutopiaproject.org/ says "all in the Public Domain or under Creative Commons licenses" https://musopen.org/ https://musopen.org/ says "free, without copyright restrictions"