Who Four hard-touring, hard-rocking Atlanta virtuosos dedicated to bringing back epic, prog-influenced heavy metal -- and concept albums, too.

Sound With insanely precise time-signature-shifting drumming, squealy lead-guitar odysseys, chug-a-chug riffs and songs that can stretch to thirteen minutes, Mastodon evoke all that is great and powerful about classic metal. "We're just all romantic about the past -- the Seventies approach to writing music," says drummer and mastermind Brann Dailor. "Bands had a free spirit to do whatever they wanted, and it was accepted." In addition to the usual suspects -- Judas Priest, Metallica, Black Sabbath -- Mastodon have more than their share of art-rock faves, including King Crimson and Genesis. They also dig country: "I fucking cried to Merle Haggard last night in the tour bus," says singer-bassist Troy Sanders.

Citizen Dick Mastodon's second album, Leviathan, is "loosely based" on Moby Dick, but wipe the sneer off your face: The aptly named band has too much lumbering power for "I Am Ahab" to be as silly as its title. Dailor spawned the concept after rereading the entire book during a grueling trip from Hawaii to London that took seven separate flights. Remembers Sanders, "Brann comes in with big bags under his eyes and goes, 'We have to do an epic album about Moby Dick.' We said, 'That sounds fucking great.' Our lives [on the road] paralleled Captain Ahab's passion or insanity." And Herman Melville's reference to the title mammal as a "sea salt mastodon" didn't hurt.

Reign In Blood The band's proudest moment may have come during its stint last year touring with Slayer, whose fans are not known for their kindness to opening acts. Says Sanders, "We never got booed. We never got hit with any beer bottles or lit cigarettes. We prevailed."