Louie's Rock City in Falls Church books a major act about once a month: showtime, midnight. That's late - even for the unconventional rock concert business. But Thursday night there was no need to worry about slipping off into premature narcosis. Rick Derringer decimated the audience with slashing guitar riffs.

Band leader Rick Derringer calls this "power pop," although it's decidedly more heavy-metal, blitzkrieg rock than pop. Ably assisted by Neil Geraldo on guitar and keyboards. Kenny Aaronson on bass and Myron Grombacher on drums. Derringer's mono-maniacal pursuit of rhythm is relentless. While all four band members join in on vocals, the potential strengths and blends of four voices are never realized as they are subordinated to the single-minded rhythmic purpose. Even Derringer's lead guitar is more a rhythmic guitar than spars with Geraldo's and then sputters in tandem until the frenzy is enough to kindle an attack of St. Vitus dance.

The one-hour set, which began with the slightly bubble gummish "Let Me In" and "It Ain't Funny," progressed to Robin Trower/Hendrix-like guitar work in "Beyond the Universe" and "Rock'n' Roll Hoochie Koo" and culminated with Derringer displaying his manual dexterity as he threw his pick in his mouth, jammed the guitar between his legs and took the instrument's neck in hand. All during this Myron Grombacher (a Johnny Rotten lookalike) jumped off the drum platform at strategic moments, mugging stupefaction, disbelief and utter admiration for Derringer's virtuosity.

By the end of the set Derringer was wet and pale having expended every inch of energy.