For most bands, a three year group between albums could be considered business as usual. For the ever-industrious Grails, the extended silence that’s followed percussionist Emil Amos becoming 50% of drone-metal duo OM a few years ago has been very uncharacteristic. Now, the renowned New York instrumental rockers have regrouped, and it soon becomes apparent that the rare breather has inspired the cult quartet to not so much re-jig their sound as to reconstruct it from scratch. The dreaded phrase “hope you like our new direction” hovers heavy over Deep Politics, like some foreboding Bat-sign, signalling the return of a band who’ve decided to rip up the rulebook and toss the scraps into the winds.

Whilst there were hints of a newfound interest in calmer moods amidst the mountain-levelling barrages of 2008’s Doomsdayer’s Holiday, the old tricks-dodging, all-change ethos of Deep Politics can initially confound. Where cast-iron guitar riffs used to reign, pianos now tinkle. The scorching guitar solos are mostly replaced by soaring string arrangements by guest star Timba Harris. Those galloping beats, capable of building a momentum not unlike an aural equivalent of an army of enraged trolls riding into a battle, are here largely swapped for the subtler charms of rhythmic repetition that resembles the kind of vintage psych-beat obscurities crate-diggers have restless dream about. Grails do funky? You’d better believe it – the chunky beats that propel the title track’s majestically melancholy keyboard theme into hypnotically mournful heights, for example, provide undeniable evidence of this unlikely – and thrilling – development.

Not that Grails have chosen to totally disregard old converts’ expectations. Although a wailing violin roams where guitars used to reign, the crunch that eerie opener ‘Future Primitive’ expands into will reassure long-term fans. Likewise, the steadily escalating high-octane dread of ‘I Led Three Lives’ will take long-time followers to familiar territory. But it’s the new avenues explored here that truly dazzle. The mini-epic ‘All The Colours of the Dark’, for example, moving seamlessly from a disjointed, jazz-influenced piano movement to a gracefully gliding guitar riff and an acoustic, deeply beautiful interlude and back again, crams more inspiration and innovation to its four minutes than most bands manage during entire albums. The late-60s freak flag flying folk rock royalty inspired ‘Almost Grew My Hair’ (note the sly Crosby, Stills, Nash & Young reference) also treks across largely uncharted territory with impressively accurate navigation.

Allow it a while to reveal its subtler charms, and 2011 model Grails soon emerges – for the most part – just as compelling as, say, the high voltage mysticisms of 2006’s desert-psych classic Burning Off Impurities.