The English band Broadcast specializes in oompa-oompa bass lines and riffs that are perfect for head-bobbing and grimy analog-keyboard drones, which hold mysteries in the overtones and harmonics. But drones can lapse into mundane vagaries over the course of a 15-song set, and the rigid 1-2-1-2 rhythm can start to sound like avant-garde polka. That hazy similitude occasionally hampered Broadcast's otherwise pumping psychedelic rock show at the Black Cat on Saturday.

Vocalist-guitarist-keyboardist Trish Keenan and multi-instrumentalist James Cargill form the core of Broadcast, but the duo was joined by a drummer and another instrument-hopper for their live show, which was heavy with songs from Broadcast's quirky new CD, "Tender Buttons." The album versions of "America's Boy," "Michael A Grammar" and "Black Cat" (which initially sounds like Altered Images' new-wave classic "I Could Be Happy" run through faulty machinery) have an advantage: a fine mix that places the band's fizzy instruments, light robotic beats and Keenan's Nico-esque voice in a proper soundstage that reveals tiny details in the tunes. But live, the drums were much heavier, the grungy instruments tended to blend together, and Keenan's projection-free voice got lost in the mix. Even though Broadcast displayed a '60s-style light show, the best thing to do was close your eyes and let the hypnotic sameness of the band's music take you into deep listening mode, where the details could be picked out -- or imagined.

-- Christopher Porter