Crack the Skye is the fourth studio album by American heavy metal band Mastodon, released on March 24, 2009, through Reprise, Sire and Relapse Records. The album debuted at number 11 on the Billboard 200, selling 41,000 copies in its first week. In Australia, the album debuted at number 19. It had sold 200,000 copies in the US as of September 2010, making it one of their highest-selling albums to date. According to an interview on the DVD The Making of Crack the Skye, this album represents the element of aether, which is represented by the souls and spirits of all things, a theme closely related to the context of the album. Because the elements of fire, water and earth have already been represented by the band's first three albums Remission, Leviathan, Blood Mountain and the band's seventh album Emperor of Sand, respectively, the element of air is the only classical element which has yet to be represented by a Mastodon album, as their follow-up studio albums The Hunter and Once More 'Round the Sun do not represent an element, nor are they concept albums. Crack the Skye is the first studio album to feature drummer Brann Dailor as the band's third lead vocalist. Musical and lyrical themes Drummer Brann Dailor described the album as more "focused" than its predecessor, Blood Mountain: "Maybe there was a deeper heart to this record that needed more exploring ... We got more involved with feeling the vibe of the record and everything feels more creepy and spaced out and something special is going on." During the composition of the record, Brent Hinds listened to In the Court of the Crimson King by King Crimson every day as inspiration, while Dailor and Troy Sanders listened to Pink Floyd's Animals. Vocalist/bassist Troy Sanders said in an interview with Stereogum, "Crack the Skye is a departure from everything we've previously recorded in the sense that we kinda strapped on our aeroshells and departed from Earth for a while, and then captained to the ethereal element of the universe and kind of slept on the roof of the world for a while to get a perspective on this record. ... Basically we're exploring the ethereal world. We're dissecting the dark matter that dominates the universe, in a nutshell." When asked in multiple interviews Dailor said the record would tell a story dealing variously with the art aesthetics