He’ll never admit it, but Tim Kinsella helped invent what we now know (and deride) as emo in 1989, when he was all of 14. The basement band he started in Wheeling, Illinois, with his brother, drummer Mike Kinsella, and two friends—guitarist Victor Villareal and bassist Sam Zurick—was a flash of furiously inspired kid genius, too artful and poppy to be properly called postpunk, and he fronted it like a wriggling postpubescent shaman. Cap’n Jazz, as they called themselves after a couple quick name changes, didn’t last long—they split in 1995 after only one album—but they were succeeded by what became an entire genre of squeaky boys going apoplectic over muscular riffs. Over the years, bands influenced by Cap’n Jazz have become more and more mainstream, but Kinsella has stayed underground, making personal, obtuse, and political records in bands like Owls, Make Believe, and Joan of Arc—usually with other former members of Cap’n Jazz.

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How is being back in Cap’n Jazz?

How weird?

The amount of physical turmoil involved now, at this age . . . I feel like I have heartburn the entire time I’m onstage. It’s intense.

You’re someone who seems to have a total absence of nostalgia, creatively and as a fan—is it embarrassing on a certain level to be part of a hugely nostalgic thing?

Of course. How I summon energy is by watching how excited people in front are. I think I am more aware of trying to be a channel for that, more than projecting out. . . .

Yes, I wanted to do a different thing for me personally—I felt trapped by it.

Headlining the North Stage, Sat 7/31, noon-10 PM, Milwaukee between Damen and Wood, 312-226-0970, $5 suggested donation.