DO THE BAD PLUS (a) play jazz music to reinvent rock? Or do they (b) play rock music to reinvent jazz? The answer might seem obvious at first, since the Minneapolis trio manned by pianist Ethan Iverson, bassist Reid Anderson and drummer David King do in fact play jazz music.

And the Bad Plus made their mark on pop culture by reinventing rock songs like Nirvana's "Smells Like Teen Spirit" and Blondie's "Heart of Glass" on their 2003 major-label debut, These Are the Vistas. These were interpretations that indie kids who had never even listened to a jazz album could understand and jazz purists who had learned long ago not to trust fusion could have their minds blown by. The band became so associated with their rock covers that they were known in shorthand as "the jazz band that plays Nirvana."

And yet the answer, as a life of standardized testing has reinforced time and time again, is probably (c), which in this case would be "both." Because the members of the Bad Plus play the music they play, the way they play it, for a reason. And their ambitions are no less than bringing jazz around to the same DIY ethic that saved rock music.

"The leader and sideman thing is pretty outmoded at this point," says Iverson of the state of jazz. "It's got to go more to guys in a garage making music."

The Bad Plus practice what they preach. The group is an exercise in band democracy: three leaders, everyone composes, everyone has a say. And while they have been praised for making jazz relevant again, it's not like they have everything figured out. In fact, the first time they played "Smells Like Teen Spirit"—at their very first live gig—it was a spur of the moment thing, and nobody thought it would turn into what it did.

"The first time we played a gig, we didn't have enough original material," Iverson recalls. "I actually didn't think it was going to work, but the minute we started I thought, 'This feels like something I've never heard before.'"

He wasn't the only one who felt that way. It wasn't like they did the first jazz cover of a rock song, or of Nirvana, or even of "Smells Like Teen Spirit." But this was different.

"One of my theories is that often when jazz musicians cover rock music, they add more or less traditional jazz harmonies to it. That somehow seems to weaken the song rather than strengthen it," says Iverson.

The Bad Plus, on the other hand, meld jazz technique and rock attitude: aggressive and percussive, bearing down at the points where traditional jazz would spin off. "We hit hard. We don't shy away from trying to push our poor little acoustic instruments as far as they can go," admits Iverson.

For the latest album, the Bad Plus have those instruments on a whole new set of songs. Though the covers get most of the attention, the Bad Plus usually play about 80 percent original material. For their latest album, though, the group decided to do nothing but interpretations. On For All I Care, the Bad Plus return to the Nirvana wellspring with "Lithium," and cover a remarkable range of songs besides: Pink Floyd's "Comfortably Numb," Wilco's "Radio Cure," the Bee Gees' "How Deep Is Your Love," Heart's "Barracuda," the Old 97's "Lock, Stock and Teardrops" and the Flaming Lips' "Feeling Yourself Disintegrate." Mixed in are contemporary classical pieces like Stravinsky's Variation d'Apollon.

This time, however, something new has been added: a singer. The band members collaborated with vocalist Wendy Lewis, who lent a like-minded rock approach to the lyrics of Kurt Cobain et al. She makes perhaps her biggest statement on "Comfortably Numb," digging into the song's progressive depths of despair while the music swirls into a haze even Roger Waters probably never imagined.

"'Comfortably Numb' we couldn't do without a singer," says Iverson. "If you play that melody on the piano, it's not going to work. It's too one-note to work as an instrumental melody."

Of course, by releasing this album, the band is once again flirting with the "jazz band that plays Nirvana" tag, practically assuring that its covers will get more attention than its original work for some time to come. Iverson doesn't mind; he sees it as part of a grand jazz tradition.

"We're improvisers," he says. "We're trying to figure out how to decode the pop culture of the moment. That's what we're here to do."

THE BAD PLUS play with WENDY LEWIS Thursday (March 5) at 7:30pm at the Carriage House at Montalvo, 15400 Montalvo Road, Saratoga; tickets are $35, call 408.961.5186.

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