OUTSIDERS: On Eisenhower, these Berklee College dropouts have toned down the jams in favor of classic ’70s rock.

“People simply can’t describe our music,” says drummer Andrew Barr of the Boston-based trio the Slip as he looks back over the band’s past decade together. “ ‘Nice’ is not the best adjective to use, but my friends who listen to death metal and classical just can’t put a finger on what we do.”

Not that dodging the fickle finger of classification hasn’t prevented the Slip — Barr, his brother Brad Barr on guitar/vocals, and bassist Marc Friedman — from racking up a club following in Boston and beyond. (Yep, they’re very big in Japan.) Fortified by the release of their eighth album, Eisenhower (Bar/None), and what’s fast becoming a hit track (“Even Rats”) on Sony PlayStation 2’s Guitar Hero II, this band of Berklee College dropouts have accomplished quite a bit with very little outside help, mainly on the live circuit. Now, for the first time, people outside the jam-band scene are paying attention to a Slip studio recording.

“This record was highly improvisational,” Brad says, speaking from New York’s Housing Works bookstore in SoHo. “We had an improv approach in the studio, like, ‘Let’s just try these sounds out. Let’s grab that thing or shake that thing.’ And though there is a place for jazz solos and we always do that as a band, now we keep it at home. On the record we found a way to convey something that feels more complete and direct.”

Indeed, their previous albums have offered playful doses of improv mixed with potent pop melodies, but Eisenhower is their most cohesive and satisfying. By toning down the jams, the Slip, who play Avalon this Saturday with My Morning Jacket, come closer to classic ’70s rock than they ever have before. Soaring melodies, flashes of overheated instrumental excursions, and a warm, retro feel in the production all combine to create a much more accessible Slip.

Brad agrees. “This time we paid a lot more attention to what it is we love about records: the way that they sound. Before we would just go along with any engineer who wanted to put mics on every drum. Here, we paid attention to getting room sounds, some space and depth and dimension.”

Fans of the Slip’s expansive live performances may be surprised by the sophistication of the nostalgic stylizing on Eisenhower, from the sun-streaked pop opener, “Children of December,” to the grandiose piano ballad “If One of Us Should Fall.” Elsewhere, Andy Pratt indulges in a little acoustic weirdness on “Suffocation Keep,” George Harrison-style slide guitar embellishes “The Soft Machine,” and there’s a Bowie-esque sheen to “Life in Disguise.” In fact, there’s so much in the way of power pop and hints of a thousand forgotten riffs that it’s tempting to wonder what happened to the jam band who once were the Slip.

“Sure, some people lumped us in with that,” Andrew Barr says of the jam-band thing. “When we were coming up in the mid ’90s, the jam-band scene was just getting started. We also played Wetlands in New York with the Sun Ra Arkestra and Soulive. But we always felt that we were not in the heart of that world. We didn’t relate.”

As former Berklee students who understood Coltrane and Charlie Parker better than they did the intricacies of “Dark Star,” the Slip found themselves perpetually on the outside looking in. “We’d be playing the Newport Jazz Festival and Scullers,” recalls Marc Friedman. “There was a time when we just wanted people to sit down and shut up. Then we realized that wasn’t the right place for the band, but we always felt like we were outsiders everywhere we went.”

“I would see lists of thousands of Boston bands and we wouldn’t even be in there,” adds Brad. “It is analogous to our whole career. Even in the late ’90s jam scene we were the outsiders. We were the weirdest of the jam bands. We played actual songs and we weren’t blatantly derivative of Phish.”

The Slip haven’t done away with their jazz chops altogether on Eisenhower, which they recorded at two local studios, Q-Division and Bubble and Squeak. But they put their instrumental talents to work where they can do the most good — in the drum solo flurry of “Children of December,” for example, and the acoustic fusion blowout of “The Original Blue Air.”

“Most jazz players don’t go on to make pop records,” Friedman says, “and maybe some pop guys go into jazz, but it was all part of our distillation process to bring it to this point. We are writing good songs that we can perform in an open way every night, and we can add creative things that keep the songs fresh. Other bands might get tired of playing their six-minute songs, but we can find these pockets of freedom.”

Although the Slip have found an entirely new audience in Guitar Hero II, they’ve rarely gotten much love from mainstream press or radio. But true to Eisenhower’s feel-good vibes, they don’t hold a grudge. Well, not for long, anyway.

“To hell with them!” Andrew laughs. “If you are in the Boston rock scene and you have leather boots and a crazy haircut, you are accepted. But it was uncool to like the Slip because we weren’t writing aggressive music.”

Brad professes no bitterness at being ignored by the critics, but he also suggests that perhaps the Slip weren’t quite ready for accolades either. “So now we have a great record, something that can win over writers who have slagged us off in the past because they know we played jazz? Those guys are looking for the next heroin addict who’s sacrificing his soul. And we never listened to punk. But I have to admit, it has taken a long time for us to figure things out. We had to go through some hard shit to write songs that meant something.”

THE SLIP + MY MORNING JACKET | Avalon, 15 Lansdowne St, Boston | December 2 | 617.228.6000

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