Primus is a San Francisco-based band formed in the mid-1980s by two ex-members of thrash metal band Blind Illusion: Les Claypool and Larry LaLonde. Les (vocals and bass guitar) has been the only constant member. They have had two guitar players (although Larry has held onto the role for the past 30 years) and many different drummers (although Tim Alexander, Bryan Mantia and Jay Lane were the only ones who recorded with the band) in the past.
These are photos from concerts where Primus played, so they may be of other bands that played the concert as well.
press clippings don't mention Sam Andrew Quartet was jam band feat guitarist co-founder of Big Brother & The Holding Company
Primus / Bedlam Rovers / Sam Andrew Quartet Oct 15, 1988 Cotati, California, United States Uploaded by Lilmikesf
review from Sonoma West Tribune of outdoor show mentioning all three bands