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Is Ponytail a rock band or an art project? Sitting backstage at DC9, the Washington, D.C., night club where the group is about to perform, guitarist Ken Seeno contemplates the questionbut not for long.

“We studied art. We like art. We want to keep art close, but we’re definitely more in the music world,” he says plainly. “I don’t want people to think of us as fine art. We are picky with our aesthetic, but it’s not conceptual.”

Singer Molly Siegel is more matter-of-fact: “It’s not some big project,” she explains with her constant smile. “To me, it’s just something interesting that’s fun.”

The Baltimore quartet’s origins would seem to indicate otherwise. Ponytail formed in 2005 in a class at the Maryland Institute of Art. The assignment was, quite simply, to create a band. As Siegel points out, such spontaneous birthing gave themSeeno, Siegel, guitarist Dustin Wong, drummer Jeremy Hymanno time to make overarching plans, artistic or otherwise. “There’s no huge theory here, there’s no way it could’ve been like that,” she insists.

I’ve asked Ponytail about their art leanings not just because of their history, but also because of Siegel’s unique vocal style. Consider the languageless mouth sounds inserted between the lyrics of today’s best art-punk vocalists: the strained grunts of the Boredoms’ Yamatanka Eye, the sharp chirps of Deerhoof’s Satomi Matsuzaki, the abrupt howls of Animal Collective’s Avey Tare. Now imagine a singer relying almost solely on such movesrarely using words, choruses or melodies. Now you have some idea of Siegel’s innovative approach. On paper, it may sound artsy or even difficult. In reality, her singing is eminently accessible, pure energy and emotion that don’t depend on lyrics to be deciphered or meanings to be misunderstood.

“My vocals are usually what makes people call our music unconventional. It seems to be the deciding factor when people don’t like our music, actually,” Siegel admits. Indeed, nearly all of Ponytail’s criticism or coverage (including this) soon enough ponders Siegel’s singing. “I can understand that because before you jump into this band, you have to know that this is the kind of vocals it has. It kind of sets it in a weirder category.” Yet what’s weird to some listeners feels completely natural to the artist.

“I don’t really know how else I could sing in this band. There’s no other way that would go with this music,” she says. “At least no other way that I would like.”

Siegel’s got a point: Her singing is uncannily responsive to the sound swirling around her in Ponytail, whichfilled with the kinetic energy of giddy crescendos and razor-sharp left turnsis just as unpredictable. On the band’s two albums, 2006’s Kamehameha and 2008’s Ice Cream Spiritual, Seeno and Wong’s frantic riffs bounce around as if played in a hall of mirrors, while Hyman’s rapid-fire drumming creates such a strong anchor that no bassist is needed. If Ponytail were to make this intricate music without Siegel providing a focal point, they might get pigeonholed as brainy math-rock.

“Having Molly thrown into the mix definitely takes some pressure off of us,” Seeno admits. “I don’t feel like all the eyes are on the technical aspects of what we’re playing. It’s more about group energy.”

An audience’s response generally validates that idea. There is little in the way of chin-scratching at Ponytail shows, as attendees typically bounce to the spastic rhythms and surround Siegel’s calisthenics with dance moves and unlikely sing-alongs. “We definitely feed off the crowd,” says Seeno. “Sometimes you can even feel beat up by the crowd if it’s a little too crazy.”

“It’s only been the past few months that [such an audience reaction] has become a standard, to the point where I get thrown off if people aren’t doing that,” explains Siegel. “In Baltimore, it happened sooner, because it is this totally great scene. But then going on tour made me realize what it was like to play to people who weren’t doing anything. That was a totally different experience. I actually kind of liked it because it was a challenge. It made me go crazier.”

That band-crowd synergy adds an air of spontaneity to Ponytail gigs, suggesting at times that the band’s tight tunes are actually improvised. “I definitely change things. I feel like I write songs on tour, that’s how I finish them,” says Siegel.

“I like when people think that the music is improvised, but it also makes me laugh, because it’s all written,” Seeno says. “We do get to the point where we’re playing the songs to such minute degrees that we can have fun with the tiniest changes that were not written into the music. It might be apparent only to us, but we really get into the little nuances.”

Still, even the craziest Ponytail tunes are filled with simple rock moves: big riffs, slamming beats, revelatory climaxes. “With some bands, if you just listen to a specific part of their sound, you can hear the melodies even in the noisiest parts. Take Fucked Upthey’re basically a pop band,” reckons Siegel, offering the Toronto punk crossover kings as kindred spirits. “I mean, they’re a hardcore band, but if you listen to the guitars, and just get into that sound, you can really feel the melodies. I think we’re similar.”

But, wait, isn’t Fucked Up kind of an art project, too?

Ponytail plays Local 506 Sunday, May 24, with Gross Ghost, at 9:30 p.m. Tickets are $8-$10.