You say the Melvins aren't heavy enough? Metallica's '80s output doesn't give you a sufficient blood-pressure spike? Fear not: Atlanta's Mastodon concocts an extreme, fist-to-the-face metallic alloy that's sure to satisfy. Less than a minute into Leviathan, the quartet's second album, Brann Dailor's hyperkinetic drums, Troy Sanders's stool-softening bass, and the axwork of Bill Kelliher and Brent Hinds have you by your scrawny throat. Leviathan is a Moby Dick-inspired concept album, and just as Melville's monomaniacal captain relentlessly pursued "the sea-salt mastodon," this foursome won't rest until their ruthless harpoon hits its mark. Sprawling, muscular tracks like "Megalodon" and "Hearts Alive" showcase the band's fierce compositional chops. But don't be fooled by all those startling, technical time changes -- Mastodon didn't come to do your math homework. This four-headed creature came to brutalize, stun and, oh, yeah, to raise your blood pressure to dizzying heights. Long live the great beast.