Here is some general information about copyright. Note: Whether the work is under copyright or in the public domain, always cite your sources! Want to ask for permission to use a work you find on the Internet? Always ask: "Do you hold the copyright for this work?"
General Copyright Overview: See U. S. Copyright Office for more information
More about music and copyright can be found at the Music Librarians Association FAQ
This information is not meant to offer legal advice
The library licenses databases so you'll have access to music resources - and then there are sites that provide open access to clips, etc. Example:
Sister Rosetta Tharpe. "Up Above My Head". TV Gospel Time - Early 1960's. https://criticalcommons.org/view?m=GWi8OxLAq
"Critical Commons is a public media archive and fair use advocacy network that supports the transformative reuse of media in scholarly and creative contexts. Critical Commons is also part of the technical and conceptual architecture of the Alliance for Networking Visual Culture and the electronic authoring/publishing platform Scalar."
Small, John. (1985, September). J. C. Bach goes to law. The Musical Times, 126(1711), 526-529. https://www.jstor.org/stable/964456
“John Christian Bach, born 250 years ago this month, is best known as one of the leading composers of his day. But he has another claim to fame ...: he brought the first legal action for breach of musical copyright… "