It’s been a month now since the Ann Arbor Folk Festival, but I still can’t get it out of my head. That’s nothing new. As a graduate student at Michigan in the 90s, the festival made for a wonderful seminar in folk music and I’m still listening to the music I discovered there. Since settling down in Wooster, Ohio, where I teach French history at the College of Wooster, we’ve made it a family tradition to drive up to Ann Arbor for the festival weekend. This year’s festival was full of great music and lots of new artists, but I can’t help recalling a performance that didn’t come off so well.

The Ann Arbor Folk Festival has become one of the town’s great cultural institutions. A fundraiser for the Ark, Ann Arbor’s wonderful non-profit venue for contemporary and traditional music, the festival brings together college kids and baby boomers, warming one of the coldest weekends of the winter. With two nights of performances and a generous definition of “folk music” that brings in country stars, bluegrass bands, world musicians, and the singer-songwriter set, the event is among the finest indoor folk festivals in the country. But it doesn’t always come off without a hitch.

I’m thinking of Jeff Tweedy’s headline performance from Friday night. His showing was a disappointing follow-up to three hours of memorable performances by Old Crow Medicine Show, the Carolina Chocolate Drops, Ryan Montbleau, Katie Herzig, Chelsea Williams, the Ragbirds, and Joe Pug. The evening ended with a fizzle. A few true Wilco fans shouted for more as the Folk Festival regulars trudged out the doors. To put it charitably: Jeff Tweedy didn’t fit the Ann Arbor Folk Festival too well.

Oh, the audience had nothing to complain about. The Friday night performances of Old Crow Medicine Show, the high-energy old-time string band based in Nashville, and the Carolina Chocolate Drops, the young trio from North Carolina, were worth the price of admission alone. Those who came on Saturday night were rewarded with mesmerizing performances from Pete Seeger and Kris Kristofferson.

But Tweedy’s performance didn’t go down too well and it’s worth explaining why. Tweedy played an hour-long set, sharing a couple new songs, drawing on some of his best-known Wilco material (“Spiders (Kid Smoke),” “I am Trying to Break Your Heart,” “A Shot in the Arm” among others), adding one song from the Mermaid Avenue Project (Woody Guthrie’s lyrics set to Tweedy’s music), and closing, with a nod to his Uncle Tupelo days, with “Acuff Rose.”

It was a solid set, if a bit low in energy. But what was most striking and disconcerting about it was Tweedy’s stage persona, which can best be described as too-cool-for-folk. Tweedy wanted to make it clear that he didn’t really belong here. “I don’t know why I still get invited to folk festivals,” he said. He offered up an acoustic version of Iggy Pop and the Stooges’ “Now I Want to Be Your Dog,” which he introduced as a tribute to the “rich tapestry” of Ann Arbor folk. (As folk appropriations go, it was a pale shadow of the Carolina Chocolate Drops take on the hip-hop “Hit Em Up Style”). He poked fun at the organizers, the audience, even at the other performers, without dropping his cool.

A lot of folk music is criticized for being overly serious. And when you hear the local coffeehouse folkie rail against bovine growth hormones you might be inclined to agree. But this night at Hill Auditorium showed something very different. It was the rockstar who was overly serious and more than a little contemptuous (“doesn’t anyone out there know what an interjection is?” he asked, in introducing “Jesus, Etc.”). On this night it was the folkies — the singer-songwriters, the old-time bands, the country musicians — who knew how to have fun.

Watching this parade of musicians, one couldn’t help but wonder just what any of this “folk music” had in common. It’s something I’ve thought about a lot in the last couple years as I’ve started playing music on the college radio station down here at (put on your radio voice) Woo91, WCWS, 90.9FM, a public service station of the College of Wooster in Wooster, Ohio. When Richard Thompson goes electric is it still folk? How about an acoustic track from Bruce Springsteen? Too easy? Then how the heck do you sort out the hundred strains of traditional music that might count as folk? And what about alt-country anyway?

Tweedy’s performance helps shed a bit of light on the question. Folk music, at some fundamental level, is about a popular musical tradition that is larger than the performer. It requires a certain amount of reverence. Depending on the band and the setting, there may be several musical traditions in the air, but the essential point remains the same. The performer at hand is filling in for the night. Someone did it yesterday. Someone else will do it tomorrow, maybe better. That’s the folk spirit: the spirit of artisanship, of craftsmanship, not tortured artistry. Sure, there are plenty of folk divas — narcissism is everywhere — but here they run directly against the grain.

One bad night means nothing for Jeff Tweedy. He’s a brilliant songwriter and compelling performer. But the funny thing here is that, for all of the tortured-rock-star pose, there’s a folky not too far beneath the surface. It was true when he was dusting off and polishing traditional tunes for Uncle Tupelo. It was true when he wrote new music to the old (and timeless) lyrics left behind by Woody Guthrie. And it was true in the words he laid down in “Someone Else’s Song.” If his music “sounds like someone else’s song from a long time ago,” it’s because he’s working right out of the center of the folk tradition.

And one ill-fitting performance doesn’t take anything away from the Ann Arbor Folk Festival. After all, it helps you appreciate everything else the weekend brings and it reminds you that there’s always something more to learn. We’ll be back for next year’s festival — and for a few shows at the Ark in the meanwhile — ready for more.

Doctor Foo is Greg Shaya, an Associate Professor of History at the College of Wooster in Wooster, Ohio and the host of the Doctor Foo Folk Hour on Woo91, WCWS, 90.9 FM, in Wooster, Ohio.