British drum 'n' bass innovator Roni Size has sprouted a family tree that rivals Pokemon in its complexity. There's his deejay collective Reprazent and his Full Cycle music company, as well as his collaborations with DJ Krush and Dope Dragon. The newest branch is his Breakbeat Era, whose live incarnation made its U.S. debut at the 9:30 club Tuesday night.

Breakbeat is constructed around the rippling vocals of Leonie Laws, who set herself squarely in the center of the stage and proceeded to pump the band through an hour's worth of tunes, covering almost all of its debut CD, "Ultra Obscene." The band's setup features what Size must imagine will be the next millennium's version of the garage band: bass, keyboard/sampler (no electric guitars, of course) and, most important, a tireless percussionist augmented with a drum machine for kicking into overdrive.

Despite monikers like "Our Disease," "Rancid" and "Ultra Obscene," the set remained rooted in the clean, skittery sound that Size captured on his landmark "New Forms" collection. Breakbeat Era veered into some darker territory, but as Laws twittered and beats splintered on "Control Freak" and "Terrible Funk," the bouncing crowd showed that no matter what it's called, the sounds are still all about propulsive, fluid motion.