Paul McCartney shared the stage with local legends on Friday night, bringing out the Kronos Quartet during his set at Outside Lands for a faithful version of the Beatles’ “Yesterday” in San Francisco’s Golden Gate Park. That surprise collaboration would be notable enough, but given the context of how rare it is for Paul to perform the classic solo tune with a string section channeling the original 1965 recording, the result was one of his more understated moving moments in recent memory. Watch a fan-shot clip above.