Check out the Smithsonian Institute Folkways Recordings

https://folkways.si.edu/

Especially those curated or produced by John Cohen and Ralph Rinzler prior to 1970. Rinzler, with Cohen, was a member of the Greenbrier Boys, one of the first urban bluegrass bands. Rinzler 'discovered' Doc Watson and successfully managed Bill Monroe's triumphant return to an urban audience after Elvis' scorching Blue Moon of Kentucky. Monroe, asked about Elvis' success later, said, "Those were some powerful royalty checks!"