Although Polvo’s sputtering music never flows as it seems it should, the songs don’t meander either, because the group’s chaos is so propulsive. The band’s fractured structures indicate high-level mathematics, but that’s not to say its odd tunings and spazzy rhythms don’t move the body. On the quartet’s third, most powerful full-length, Exploded Drawing, a new embrace of melody colors its art-rock outlines, and the exploded view shows Polvo to be something more than sound scientists. Producer Bob Weston boosted the not-at-all-embarrassing vocals and lyrics of guitarists/crooners Ash Bowie and Dave Brylawski, providing euphonious lines that anchor the band’s swaying songs. With Pipe and Wingtip Sloat at 8:30 p.m. at the Black Cat, 1831 14th St. NW. $6. (202) 667-7960. (CP)