Now one of the biggest bands in metal, Mastodon have constructed their reputation as demi-gods over the course of the last decade with apparent ease. Their last album - 2006's 'Blood Mountain' - practically received a clean sweep of critical accolades, placing the Atlantan quartet in a prime position to build on their success.

'Crack the Skye', their fifth studio album, does just that. For long-time Mastodon fans and newcomers alike, it's as accessible a metal album as you'll hear these days, and even musos who've previously turned their noses up at the genre may find something to appreciate here.

With two concept albums under their belt, rumours that 'Crack the Skye' would be based around enigmatic Russian monk Rasputin proved unfounded; instead, according to the band, the topics covered are related to 'astral travel, Stephen Hawking's theories, wormholes in the time-space continuum' and other abnormalities. In other words, not exactly your typical inspirational source material for metal-heads. Musically, noted producer Brendan O'Brien (Pearl Jam, Springsteen, Rage Against the Machine) does a great job of prying open the heavy, intense riffs, subsequently leaving space for the songs to breathe and for intricacies and atmosphere to develop between the lulls - 'Oblivion' and 'Divinations' are good examples of such a method.

But this is no soft, sensitive new direction for the foursome. With seven tracks stretched over 50 minutes, most songs contained within 'Crack the Skye' are executed with a thoughtful, furious urgency - thirteen-minute closer 'The Last Baron' is typical of the erraticism in tone and tempo that is somehow neatly pulled together. True, it sidles up to prog a little too comfortably on a few occasions, but nevertheless, 'Crack the Skye' sees Mastodon deliver the goods.