"The New Monk was SRO and when they began playing, the crowd couldn't sit still. Garcia also did some singing. They got together some bluegrass (which Garcia is known for), gospel and rock" (Staska and Mangrum 19710701). NB also Merl Saunders and Friends at KK the (Friday) night before - probable Garcia was there. Tom Fogerty's first single was coming out around this time - could it all have had a marketing aspect? Fogerty also listed in SFE.
Listing: "The Music Scene--Complete Listings," San Francisco Chronicle, June 25, 1971, p. 43