This year, San Francisco’s Outside Lands Festival scored a coup. Paul Simon retired for touring after finishing up a big farewell tour. But he said that he’d still play shows every once in a while to raise money for environmental charities, when the situation was right. And last night, Simon headlined the last night of Outside Lands. (Other than a Friday-night Outside Lands warm-up show at Oakland’s Fox Theater, this was Simon’s first full show since he ended the farewell tour.) During his encores, Simon brought another ’60s legend to the stage.

Onstage at Outside Lands, Simon said that he’d known Bob Weir, co-leader of San Francisco greats the Grateful Dead, ever since 1967’s Monterey Pop Festival. But he also said that they’d never actually played or sung together. So last night was a first. Weir and Simon stood side-by-side onstage and sang “The Boxer,” Simon And Garfunkel’s tingling, immortal 1970 song.

Simon and Weir duetted toward the end of a 21-song set that spanned Simon’s entire career, including three Simon & Garfunkel songs. (The experimental string ensemble yMusic joined Simon for a few songs, including a take on “Bridge Over Troubled Water.”) On “The Boxer,” Simon and Weir sounded lovely together — even in the one funny bit when Weir jumped the gun on the chorus. Watch a fan-made video of their performance below.

Maybe those two will join each other onstage again 52 years from now. Probably not, though.