Additional personnel: Richard Morris (Mellotron, synthesizer).

Audio Mixer: Brendan O'Brien.

Audio Remasterer: Bob Ludwig.

Atlanta's Mastodon climbed to the top of the metal heap the old-fashioned way. Taking the template for success etched by Metallica, the band captured the imagination with a series of albums that offered potent heaviness and relentless experimentation. After graduating from respected indie Relapse, they released 2006's acclaimed BLOOD MOUNTAIN, an album with a fire motif/fantasy adventure concept that opened numerous doors both commercially and critically. Their latest, CRACK THE SKYE, completes their elemental cycle by focusing on "ether," while also serving as a tale of czarist Russia. The progressive metal elements that bled into their sound on BLOOD MOUNTAIN are pushed even further here, led once more by Brann Dailor's furiously technical drumming. As Dailor goes, so goes the band, and his stick work remains some of the finest this side of Neil Peart. The crackling "Divinations" follows up the contemplative, restrained "Oblivion" with furious thrash riffs and springy dueling fretwork, and "Quintessence" wraps glittering guitar arpeggios around Dailor's impossibly percolating drums. The four-part "The Czar" is a towering epic that comes off like Rush on steroids, each part with its own distinct feel. A more mature and adventurous metal album is unlikely to be heard for a long time.