Performance art has a reputation, not entirely undeserved, as the opposite of entertaining.

So what to make of Ragnar Kjartansson, who's definitely a wacky performance artist -- he's sung songs for days on end in an abandoned theater -- but also a born entertainer?

In other words, should we be glad that a man jouncing his he-boobies is considered art fit for the stage of the Carnegie Music Hall?

Kjartansson, 34, is the internationally feted Icelandic artist whose exhibit at the adjoining Museum of Art included last night's performance. Kjartansson had billed the show as "Ingmar Bergman-style vaudeville," though what that meant was largely a matter for personal interpretation. We knew only that it would involve Kjartansson, some family members and friends, and music.

The curiosity factor must have helped. The show -- a joint production with The Andy Warhol Museum's Off the Wall series -- drew some 400 folks, by my estimate. The performance actually began in the music hall's grand, marbled lobby, where eight local guitarists has been recruited by Kjartansson to perform the same chord progression for a couple hours straight while strolling about (even while no one else was around). The musicians had been asked to wear pajamas and drink beer, though not all had complied with the former request.

On stage -- alongside a big stuffed lion (the Warhol's, I think) -- longtime Kjartansson collaborator David Pór Jónsson began with a lengthy piano improvisation. It was impressive, ranging from classical airs to loungey interludes. Most of the show, in fact, was music, including several charming, dark-humored little original ditties played as a two-guitar duo by Kjartansson and Pór Jónsson.

They even paid tribute to Pinetop Perkins, the 97-year-old bluesman who died this week -- a bit eerily, just weeks after Kjartansson's video honoring him went on display at the Carnegie. (Perkins "started smoking in 1921 and died Monday," Kjartansson reminded us.)

At its best, the evening truly had the feel of a living-room get-together, as Kjartansson had promised in interviews.

So where was the "performance art"? You know, the concepty stuff?

Well, there was this "melodramatic play" (Kjartansson told us) written for the show by his wife, Ásdís Sif Gunnarsdóttir. It was in four or five scenes interspersed throughout the evening, most of them involving Gunnarsdóttir playing a sort of tortured artist.

At first, even knowing Kjartansson's impish humor, you were inclined to take the play straight ... by which standard it was deadly performance art of the sort everyone fears: pretentious, impenetrable, etc. (At one point, after reciting some terrible poetry, Gunnarsdóttir flicked on an overhead projector and sort of scribbled on it.)

So this was a joke, right? Had to be. Except it wasn't over the top enough to be funny ... unless it was instead some sort of Andy Kaufman-like exercise in audience discomfiture. But that wouldn't really fit Kjartansson's style.

Regardless, most of the audience stuck around after intermission and really got the better of the deal. Especially, this involved the extravagantly bearded Kjartansson and Pór Jónsson appearing respectively in the balcony-boxes above either wing of the stage, clad in gladatorial breastplates and, wielding electric razors to the strains of heroic symphonic music, shaving their faces clean down to the mustaches. Now that's performance art you can dance to.

The encore ended with Pór Jónsson on piano, accompanying Kjartannson for a set of German lieder, or art song. Kjartansson's a passable singer, and the melodies were quite lovely. So of course beefy Kjartansson crescendoed by peeling off his shirt and concluding with the aforementioned burlesque move -- a sight few will forget, no matter how hard they might try.