Mastodon’s debut full length, Remission, was a heavy, sludgy album that was an instant underground classic for metal fans. But it was heavy enough to be near inaccessible to casual metal fans, despite the drum calisthenics of Brann Dailor and the fluid but heavy guitar work from Brent Hinds and William Kelliher. The vocals were screamed much more than sang, and despite the complex riffage, it seemed like the band had would be comfortable opening for bands like The Dillinger Escape Plan and Clutch and building up their reputation as a great live act. Instead, after a solid few years on the road, they reconvened with producer Matt Bayles and recorded Leviathan. It was more of everything: the heavy songs were heavier, the proggy songs (like the 13:39-long ‘Hearts Alive”) were way proggier, and while the band didn’t totally forsake the screamed vocals, there was more melody on the album. It even had more of a theme. While Remission was apparently about earth, Leviathan was about Moby Dick.