A Julien Baker show is a powerful, almost religious experience, and a big part of the reason is that she’s the only person onstage for most of it. Right now, Baker is on tour with Boygenius, her supergroup with Phoebe Bridgers and Lucy Dacus. But when she’s performing her solo set before the Boygenius encore, the only person who joins Baker onstage is Camille Faulkner, her violinist. Thanks to effects pedals and loops and her own titanic voice, Baker never sounds small, but that show is just her, on guitar or piano. On Friday night in Los Angeles, she broke away from that for long enough to introduce a fellow titan of moody indie rock.

The National’s Matt Berninger joined Baker to perform “All I Want,” a song that he contributed to American Chaos, a documentary about the time just before the 2016 American election. Berninger wrote and recorded the song with the film composer Steph Altman, and he also recorded a duet version of it for a forthcoming 7″ single that’ll benefit Planned Parenthood. Berninger and Altman, as well as a drummer whose name I didn’t catch, performed the song with Baker.

Given the subject matter and the people involved, you could probably already guess that it’s a stark, heavy-hearted song. Berninger and Baker both have big voices, but they’re very different from each other, and they work together in interesting ways. They make an intriguing physical pair, too; Berninger’s at least a foot taller than Baker, though he never overshadows her. Watch a fan-made video of the performance below.

American Chaos is showing in a couple of theaters right now, and I guess that 7″ will be out in a couple of weeks, though it hasn’t been announced yet.