Many a jazz historian has pointed to Miles Davis’ 1970 release “Bitches Brew” as the moment when rock entered the jazz world. And while the influence of rock undoubtedly pervaded Davis’ music from that point until his death, a contemporary jazz group, the Bad Plus, is exploring a new way of combining two of America’s most prominent indigenous musical forms. The trio, which has created a buzz with the unique sound of 2003’s “These are the Vistas” and 2004’s “Give,” will play a double-bill with guitarist Bill Frisell on Friday at the Chicago Symphony Center, 220 S. Michigan Ave.

Just glancing at the Bad Plus’s two studio releases and the 2005 online-only release “Blunt Object: Live in Tokyo,” even the casual observer would be startled by the presence of non-jazz material, which includes Nirvana’s “Smells Like Teen Spirit,” Aphex Twin’s “Flim” and Black Sabbath’s “Iron Man.” The Bad Plus’s covers and original compositions reflect the group’s varied influences.

“We’ve had very different life experiences and dug different types of music,” says pianist Ethan Iverson. “No one of us has to know everything to make it work. We just have to know what we need to know, and then the three energies hopefully align and we feed the information through the system, the machine that’s the three of us. It comes out sounding like the Bad Plus.”

In fact, the “Bad Plus sound” has been the subject of much discussion surrounding the jazz trio. According to bassist Reid Anderson, the band takes interest in how others label them. He says he particularly enjoys the description of the Bad Plus as “avant-garde populists.”

Avant-garde tendencies definitely find their way into the band’s sound, but ignoring Anderson’s frequent use of the bass as a melodic instrument, and what Iverson refers to as a “cinematic nature” in the band’s sound, would leave the listener with an incomplete picture. In terms of musical genres, the Bad Plus merges the spirit of the avant-garde with the rhythmic tendencies of rock ‘n’ roll, the improvisational sense of jazz and the melodic style of classical music.

Anderson and drummer David King grew up listening to rock and pop music, while Iverson did not. Iverson explains his view on the melding of the Bad Plus’ influences.

“A lot of our melodic writing or structural considerations might be the influence of classical music,” he says. “Certainly there’s the influence and a really deep knowledge of rock and pop drumming from Dave, which I think is a really significant feature, in that when we do play a back beat or something, it’s very genuine from Dave.”

The Bad Plus clearly feels at home in the domain of rock, a trait Anderson sees as lacking from much of the jazz world.

“A lot of times there are certain hang-ups, or people feel like they have this responsibility because they’re playing ‘jazz,’ capital ‘J,'” he says. “They exclude certain influences or they don’t let certain things come out in their music that are actually a part of who they are. A lot of jazz musicians grew up listening to rock music, for example. But that doesn’t really come through in their music, partly because I think that they’ve put so much energy into jazz and the idea of jazz that they don’t want to dilute it.”

In addition to exploring musical territory outside jazz, the Bad Plus also operate in an unconventional manner for a jazz group: They have no designated leader.

“The Bad Plus is an environment, and has been from the beginning, where we’re really allowed to do what we want,” Anderson says. “The whole process of creating that sound has been really done without any premeditation. It’s just a situation of three people that know each other well and really respect each other and really enjoy what each other does when they’re most being themselves.”

Perhaps the Bad Plus prove the most “themselves” by recording their music live, without the aid of dubbing techniques. While the liner notes of “Give” do mention two instances where the band made substitutions from previous takes, the band makes it clear that neither album has featured any overdubs. But the Bad Plus’s choice to work with Tchad Blake, a producer who has been at the helm of recordings by Phantom Planet, Pearl Jam and Los Lobos, might give listeners a different perception of the recording process. Iverson explains the group’s feelings on the way they record.

“We have a certain pride in making the music happen like that, in the moment, just as we do live,” Iverson says.

Playing various melodies in the moment and being able to improvise on the piano might be commonplace for Iverson these days, but the pianist admits he was at a much different place musically in 1989, when the trio first played together and Iverson claims he was “learning to play” his instrument. After traveling along their own paths musically for 11 years, the trio reconvened in 2000 and things were different.

“We finally did a gig in Minneapolis as a trio, and we really felt like, ‘Oh boy, this is something that could go,'” Iverson says. “We formed and then it all moved pretty fast for us since then.”

Even though they’ve only been together for five years, the Bad Plus has carved out its own place in the evolution of jazz. Anderson reflects on his band’s place in the rich history of the music as a “true band.”

“I think that we’re not the only example, but there’s a very small handful of true bands in the world of jazz right now,” he says. “The economics and logistics and leader-centricity of the jazz world have hurt the music. There are any number of reasons why the same group of people don’t stay together and make music. But historically speaking, that’s been the best music, bands like the John Coltrane quartet or Miles Davis (and) his two famous quintets. That’s where the music really came together and had a sound of its own.”

And just like their predecessors Coltrane and Davis, the Bad Plus have created what is truly their own sound.

Weinberg junior Sam Weiner is the PLAY music editor. He can be reached at [email protected].