"I'm a child of the '70s," Phish frontman Trey Anastasio tells us in his band's documentary, Bittersweet Motel. "I didn't grow up listing to Del McCoury and the blues. I lived in New Jersey and went to the mall. . . . The middle-class suburban white kid is a part of American musical history. Like it or not." The goof-rock guitar hero's got a point there. But while the Phish guys certainly come off in the film as genial products of the American burbs, director Todd Phillips (of, believe it or not, the graphic G.G. Allin doc Hated) fails to make a case for them as a band of musical visionaries, or as a group of intriguing personalities, or as performers worthy of their doting cult audience, or even as subjects who can hold your attention for the course of an 80-minute film. Phillips tracks the band in 1997-'98 through arena gigs in the States, club gigs in Europe, and a massive festival in rural Maine, capturing performances of fan favorites such as "Wilson," "Tweezer," and "Loving Cup." He tags along with the musicians while they rehearse, hit the beach, and, improbably enough, go gun shopping. If you're a Phish fan, no negative-critic vibes will keep you away; if you're puzzled by the whole Phish phenom, nothing here will clear things up. Warning: The film contains lots of pale, unlined, naked hippie flesh. Very, very pale. Opens at the Charles Theatre Sept. 15.