It would seem that the negative stereotypes of prog are falling to the wayside, as artists from all genres are inching more and more into the no-fly zone of progressive. The Decemberists jumped into the deep end with their latest, and metal-masters Mastodon further entrench themselves with their most proggish album yet. On Crack the Skye, Mastodon presents itself as a full-on progressive metal entity, the echoes of early Metallica that resonated strongly on Leviathan are much more subdued. You should expect as much, looking at the absolutely over-the-top album artwork (I hope the guys are as big fans of Big Trouble In Little China as their Lo Pan-ish imagery suggests).
To a large extent, this move farther towards the progressive was inevitable when considering Mastodon’s catalog and approach. With a historian’s measure of exactitude and the flourish of a great novelist, they have always crafted epic tales, grander than most in the genre topically, and nearly all technically bombastic without overstaying its welcome. Leviathan drawing no trivial amount of inspiration from Moby Dick, or the epic fantasy of Blood Mountain. Crack the Skye edges towards decidedly more sci-fi fare, interdimensional and inter-temporal travel being lynchpins to the pseudo-plot.