Jerry Garcia’s idea of taking a break from the Grateful Dead was to play music with other people. Of the many aggregations with which he moonlighted, none is so revered as the various outings he made with organist Merl Saunders in the early ‘70s. Their relationship was particularly simpatico, and the small Keystone Berkeley was as close as they came to having a home base. This set features one of Garcia-Saunders’ most stable and potent lineups, with bassist John Kahn, Dead drummer Bill Kreutzmann (the only surviving member) and saxophonist/flutist Martin Fierro, extending—as they were wont to do, for upward of 20 minutes or more—a fairly typical mix of tunes stemmed in R&B, blues, reggae and rock. Among the highlights is a rare workout on the Four Tops’ 1973 Top-10 hit “Ain’t No Woman (Like the One I’ve Got),” slowed to mid-tempo for plenty of individual expression and close interactivity. The quintet grooves along easily, gradually tucking in new themes until around the five-minute mark, when Garcia decides it’s time to break loose, unleashing a brief but magnificent solo and then stepping out of the way for Saunders to do the same. A kicking take on Junior Parker’s “Mystery Train,” a sensitive reading of The Band’s “The Night They Drove Old Dixie Down” and an especially funky “The Harder They Come” (from the same-named Jimmy Cliff Jamaican film) are among the other peak moments of a keeper of a live show that demonstrates—not that proof was ever needed—Garcia’s insatiable desire to keep pushing the envelope.