The Band (211
songs)
The Beatles (1696
songs)
Peter Green (270
songs)
The Rolling Stones (469
songs)
Traffic (103
songs)
I happened upon Desert Rain in August 2015 and was floored by the number of different songs they've covered over the years, not just for the bands I've collected, but songs by other groups as well—and in addition to their own originals. There seems to be an even mix between Beatles and Rolling Stones covers, with a couple each from The Band and Traffic, plus Peter Green's "Black Magic Woman".
I enjoy their performances, experienced vicariously via their downloads. I didn't look closely at the recording setups, but some of the tracks are marred by crowd noise, so I suspect there weren't many soundboard recordings. The group's vocals aren't the greatest, but that often depends on the song as sometimes the vocals fit right in and are very effective (and affective!). Kudos to Jan Goldstein, John Kneeland, et al.!