Great music few are aware of. Any genre.

Muleskinner--the quintessential hippie bluegrass band.  They made one album and there is an audio recording available of a local PBS TV appearance (probably wasn't called PBS yet, but...)
Peter Rowan, Clarence White, David Grisman, Bill Keith and Richard Greene.  Man, what a band!

Yes! The Muleskinner album is fantastic, and that live TV appearance was put out on VHS tape. I don't know about DVD. Speaking of Peter Rowan, he joined Seatrain in time for their second album (s/t, produced by George Martin), and the version on that album of Lowell George's great song "Willin' " is my favorite.

Recent find for me is Steve Howell. Acoustic folk style blues, pre-war blues/jazz.

Here's a great one...

Jon Snodgrass  "Visitor's Band"

The Asylum Street Spankers from Austin TX, part Texas swing, part vaudeville, astonishing musicianship and all acoustic. Sadly they broke up about 5 years ago, they never quite made it. Quite a few of their releases are on Tidal the rest Bandcamp.