This is interesting, from the liner notes: "In December 1970, Saunders replaced Howard Wales at a weekly jam session with Garcia, bassist John Kahn, and drummer Bill Vitt at the Matrix in San Francisco. The audience grew over time until the place was packed every week. Saunders taught Garcia standards like "My Funny Valentine" and "Georgia On My Mind," and the pair bonded over John Lennon's "Imagine." Quoted in Blair Jackson's excellent biography Garcia: An American Life, Jerry said: "I'd never played any standards; I'd never played in dance bands. I never had any approach to the world of regular, straight music. He knows all the standards, and he taught me how bebop works. He taught me music.""
That last sentence is a little hyperbolic, IMHO; Garcia seemed to be doing just fine up until that point. But Saunders led him to expand even further.
I tend to have a rule of listening to the music first before reading the liner notes on my LPs and boxsets.
I am about halway through the set, I might have to break my rule.