Etched on the matrix groove of "Outside Inside," the Tubes' latest record: "And what's that? That's not the Tubes!"

Oh, of course it is. It's just that their music has been through so many reincarnations that it's lost all identifying characteristics. Over the decade, THE TUBES have Ping- Ponged from Genesis to Kansas, at the moment coming to rest at Boston, which is exactly who they sound like on their new single "She's a Beauty." Who'd have expected it from the band that gave us "White Punks on Dope?" This is the kind of synth-laden light metal that teenage guys always crank to distortion at the pool. They like those fuzzed-out power chords, those adolescent harmonies, those macho eternal verities about girls in the lyrics. Actually, it's fairly catchy stuff in a mediocre, predictable sort of way. The high is the single, the low a funk- stripped cover of Curtis Mayfield's "Monkey Time," on which guest singer Martha Davis (of the Motels) shows just how obnoxiously hambone she can get. Everything else falls somewhere in between. THE PLIMSOULS are another well-intentioned L.A. power pop quartet who can't get past their derivations to their identity. Their aptly titled new album, "Everywhere at Once," is cheerful, competent and instantly forgettable, mainly because they try to cover their lack of imagination by drawing from too many sources at once. The highlight here is "Oldest Story in the World," a dead- on Bad Company imitation, only louder. ON RECORD, ON STAGE THE ALBUMS THE TUBES -- Outside Inside (EMI ST-12260). THE PLIMSOULS -- Everywhere at Once (Geffen GHS 4002). THE SHOW THE TUBES/THE PLIMSOULS, Saturday at 7:30 at Merriweather Post Pavilion.