"It's got a funky beat and you can dance to it," says String Theory bassist AJ Noto. OK, sure, lots of things do. But bluegrass?

The answer is yes, especially when you're talking about the boys in String Theory.

Since February, this local bluegrass quartet has hosted a bluegrass open jam every Tuesday at Johnny's Irish Pub, with musical hopefuls lining up with instruments in hand to play with the band. And when the band's not backing them up, it chugs on its own, churning out music in a blurring acoustic flurry on a stage that looks more like a windowsill.

On one of these recent Tuesdays the place was packed with revelers, drinkers, barflies, and musicians. The band's sound ebbed and flowed between the conversations' cracks. Then the group cut into Talking Heads' "Life During Wartime" and ears perked up, eyeballs shot to the stage.

People like to hear stuff they're familiar with, no doubt. But this was a kind of a stretch - and a pretty cool one at that. It wasn't as weird as you'd think. It made perfect sense actually, as if it had been written this way in the first place. When you think about it, morphing a rock song into bluegrass is theoretically more feasible than switching it to, say, reggae or jazz. Going to bluegrass, the tempo and phrasing of every instrument is goosed and tweaked, not just the beat.

"Twisted covers" is what banjo, fiddle, and guitar player Mike Kedley calls them. Or as his brother, guitarist Terry Kedley, puts it, "bluegrass with a rock tinge."

"We mix in a little blues, a little reggae, a little jazz, a little salsa, meringue," Terry says. "We like to keep people on their toes. Plus with Mike switching between banjo, guitar, and fiddle, it's kinda three different sounds."

The band's instrumental juggling helps keep the cobwebs clear and the music less one-dimensional.

"For some people, a whole night of bluegrass may weigh on their nerves a little bit," says Terry. "We open it up a bit for more people to enjoy."

And proof that String Theory is on the right track, purist panties often wind up in a bunch.

"When we go to the bluegrass festivals people look at us like we're a bunch of freaks," Terry says.

"I think we piss off the purists anytime we play," mandolin player Jim Barbero says.

Maybe it's the Talking Heads or the Metallica. Maybe it's the band's casual, just-rolled-outta-bed attire. Maybe the detractors are just jealous. Because man, all four of these cats can play.

String Theory can get trad, too. No percussion is permitted at the open jams and nothing gets plugged in. Period.

It's an open door for the oddballs, though. String Theory gets a parade of musicians signing up to sit in with nose flutes, kazoos, washboards, and jugs.

"Bluegrass is like the blues," Terry says. "If you can play it, you can play it with anybody."

When you think about it, it's really hard to not enjoy yourself around bluegrass music. It's upbeat, frenetic, frantic, and exciting. The mood is perpetually up.

There are the occasional social misconceptions. "Every time someone hears a banjo, they wanna paddle faster," Noto says.

Though this line-up has been around for three years, String Theory has yet to release an album. The members cite the live show's elusive energy and the uncomfortable confines of the studio as reasons for the delay. The Kedleys see it more as keen marketing.

"It's part of our mystique," Terry says. "You can't take it home with you. You've gotta come out and see us."

"If you want CDs," Mike says. "You gotta see deese guys August 9."

String Theory opens for New Riders Of The Purple Sage Thursday, August 9, at the High Falls Festival Site, at 5 p.m. www.stringtheorybluegrass.com.