When it comes to At the Drive-In offshoots, the members of Mars Volta have a lock on conceptualizing unexpected detours into weirdness. But Sparta gives the prog freakers a run for their money on Porcelain, a second album that bends the boundaries of screamo, metal and punk with a little experimental action of its own. Detached electro clicks perforate the intro and ghostly interlude of "Tensioning," and singer Jim Ward resembles Mark Kozelek as a futuristic metalhead on "Lines in Sand." A yawning highlight and steeped in the bombast of towering guitar spirals, the latter bears a vague resemblance to Guns N' Roses' "Estranged." Still, like Sparta's first full-length, Wiretap Scars, Porcelain thrives on contrast: "Travel by Bloodline," a pummeling yowl, moves directly into "P.O.M.E.," a jazz-inflected, 47-second drum interlude, which is followed by "Guns of Memorial Park," a metal song imagined by hardcore heroes Thrice. Although the sprawling, challenging album might throw off some listeners, Porcelain harnesses its aggression in creative and exciting ways.