Even before the house lights had come back on at the end of Chairlift's opening set, someone in the crowd was whistling the melody from "Young Folks." Years later, the song is still endearing, and so is the band. Since "Young Folks," Peter Bjorn and John have released a neat instrumental album, been sampled, and then befriended, by Kanye West, and won the equivalent of a Grammy in their native Sweden. But their presentation is as casual as ever: when the stage went dark again, it revealed a black light backdrop with the band's name written at the top in their favorite scribble-font; below that, the word "Backdrop" repeated like wallpaper. The screen printed T-shirts for sale in the lobby read "Peter Bjorn and John T-Shirt." Guitarist Peter Moren took to the stage in a swanky blazer, followed by bassist Bjorn Yttling (in a leather jacket), and drummer John Eriksson (in a hula hoop of some sort, among other things). Thus appointed, the band kicked off a set in which even their most immature tunes were updated with startling verve and grandeur.

Foremost among these was "Living Thing," which turned into an energetic cross between "Not Fade Away" and "The Lion Sleeps Tonight." Second place goes to "Object Of My Affections," if only because of its audience participation segment, which somehow actually had everyone clapping on the correct beats. "Young Folks" didn't fare nearly as well; ever heard several hundred people try to whistle in unison?

"Lay It Down" drew some cheers with unruly lines like "Shut the fuck up, boy/You're starting to piss me off." But it wasn't a fight song, or at least not a serious one -- it was a party anthem, the sort of drunken spat between friends that gets worked out the next morning over hangovers and cold Pop-Tarts. Carpe diem, kids; even the worst memories from the best years of your life are worth holding onto. The carefree escapism of outings like this are precisely why everyone cares so much about this band: funny accents, glittery streamers glued to the instruments, and pretty soon swine flu just evaporates into the two girls dancing up front wearing skimpy pink piggy outfits and surgical masks.