Bob Weir served as the special guest at this past weekend’s Sound Summit festival at Cushing Memorial Amphitheatre near the summit of Mt. Tamalpais overlooking Weir’s home base of Mill Valley, CA, and along with his previously reported sit in with Herbie Hancock, the Grateful Dead guitarist also joined Grace Potter during her set for “Friend of the Devil.”

Potter and her band welcomed Weir to the stage for the Dead classic, with both of them sharing vocals on the laid-back version of the tune. Watch a video of the collaboration below, courtesy of Deadheadland.

Next up for Weir is next week’s Get Down to Earth event for the Green Schools Alliance in San Francisco, before a stop at the inaugural Sweetwater in the Sun festival followed by his tour with new project Wolf Bros, kicking off in mid-October.