From Wikipedia: "The company was founded by Owsley Stanley as a workshop in the rehearsal room of the Greatful Dead in Novato, California, near San Francisco, to help improve the entire sound chain for the band's live recordings, from instruments to PA. Soon the group was active in sound recording, modifying and repairing guitars and basses, and PA systems."
"During 1969 we developed the Alembic electronics and pickups. We first installed them in David Crosby's 12-string Guild guitar (which he still uses to this day) and then into Phil Lesh's SG bass that had been hand painted by Bob Thomas in his trademark renaissance/psychedelic style. After several more experimental designs, both Phil Lesh's and Jack Casady's hollow-bodied Guild basses were renovated with new low-impedance pickups and new active electronics. Bobby Weir's and Jerry Garcia's guitars were done as well."