Sitting in his dressing room after an early performance at Cambridge's Nightstage last weekend, Dave Herlihy sounds like a man on the fringe. He blasts the pop music establishment with words that could easily have come from a disgruntled starving musician, a victim of the corporate interests which dominate the music industry.

"Most popular artists aren't interested in doing anything worthwhile," he complains. "I don't want success on any terms. I don't care about being a guy in leather pants with no underwear," he says.

But Dave Herlihy and his band, O-Positive, are far from the fringe. After years of playing the local club scene, the band recently released their first album with Epic Records, and this week opened for Sinead O'Connor concerts at Great Woods. Now, with their first video getting airplay on MTV, O-Positive seems on the verge of making the big breakthrough to the elusive Mainstream.

Despite the band's recent popularity, Herlihy's retains his "fringe" voice, a rebellious testament to the postmodern contradictions which embody both the band's music and its success. In some ways, O-Positive seems to be the beneficiary of a true establishment success story: via "musical survival of the fittest," O-Positive stood out from dozens--maybe even hundreds--of struggling local bands to win the recording contract they deserved.

But on another level, O-Positive is the exception rather than the rule. They are the band that struggled for years as a local favorite, with little or no recognition on the national scene. With the release of their second album on an independent label, they earned a loyal following. They were able to channel this support into radio airplay--first on college stations and then on commercial stations. Soon O-Positive broke into the mainstream in a way few of today's mass-produced, pre-fabricated pop stars do.

Because they are in the unusual position of being a nationally known band that still plays local clubs, O-Positive is free of the reputation and "sound" which burden so many mainstream groups--they can sport a casual disregard for the pop music establishment, while unashamedly accepting its rewards. "We just play what we like," Herlihy says. "We dont try to write songs for anyone else."

Herlihy's words, his disregard for the demographics which so obsess record promoters, echo a sentiment that performers frequently express. "We haven't really worried about how [our music] is going to be received," he says proudly. "We just try to get ourselves excited about it."

What distinguishes Herlihy's words from those of so many other defiant pop stars is the music that backs it up. At first listen, O-Positive sounds like an REM clone--a fact which Herlihy attributes to the similarity between his voice and the voice of REM's lead singer. But O-Positive is more than just another post-pop band with whiny and slightly off-key lead vocals.

Thoughtful lyrics and interesting chord changes serve to establish the band's musical credibility. But what sets O-Positive apart is their synthesis of eclectic musical styles and sounds into a logical, although seldom highly-polished, product. Herlihy prides himself on the ability to use musicians such as violinist Peter Rhee and trumpeter Artie Barbato in a way that transcends a token nod to the non-guitar musical universe.

"Hope the Boat" --the opening chords of which are a dead ringer for those of Al Stewart's "Year of the Cat" --uses real rock violin, not just classical violin juxtaposed with a rock beat. And in "Overflow," Herlihy plays the socket wrench, with intriguing results.

Perhaps the greatest testament to O-Positive's eclectic embrace of diverse musical genres is "Innernational" --a dance tune with a synthesizer-driven baseline that exposes most current dance songs for the amateur efforts that they are. The song--which Herlihy described in concert as "a political song that's not about parties" --engages Barbato in an all-out trumpet-synth jam which is nothing less than uplifting. "It isnt just `Do me baby, take off your clothes'," Herlihy says, comparing his song, which includes the line "No Das Kapital," to current dance hits. "I don't want to do a dance song like that."

The song's success goes beyond its obvious pop appeal. With "Innernational," Herlihy succeeds in creating a good dance song, distinguishing between his distaste for current pop and the concept of pop music itself. "I love pop music. Rather, I love what pop music could be," he corrects himself. "Top-40 should be cooler than it is."

The apparent contradictions which pervade O-Positive's music are even present in the band's promotional material. Stephanie Bucci, the band's publicist, explains in a press release that the name of the group's new album is representative of themes present in their music.

"`Toy Boat Toy Boat Toy Boat' is symbolic for the album in that it conveys an unexplained innocence a child has when he's growing up," the announcement matter-of-factly explains. "Everything is new to a child, all uncharted waters."

Herlihy, however, tells a different story. "It's just a tongue twister, you know," he says, demonstrating the title's difficult pronunciation. "We just wanted to have some fun. We wanted to hear the deejays say it, like they're chewing molasses."

Despite the bands' denials, there is meaning in O-Positive's music. And that meaning comes not only from the music itself, but also from its contradictions. In an industry that insists on predictability and continuity, O-Positive's eclecticism defies all the rules. But, as Herlihy puts it, perhaps that is what is needed to restore pop music to "what pop music could be."