This fourth album from Peter Rehberg and Stephen O’Malley finds the duo upping the ante considerably in terms of grim, hellish and agonisingly slow guitar- and electronic-led drones. Moonlighting from his day job as half of Sunn O))), O’Malley turns away from that group’s relentlessly sludgey twin-guitar attack in favour of more silvery, melancholy tones. Rehberg, for his part, makes scalpel-sharp electronic incisions to take the music ever deeper into uneasy listening territory.

Much as I admire Rehberg’s solo work as Pita, I have to admit that this collaboration lends a powerful extra dimension to his music. The icy fog of O’Malley’s guitar provides a queasy counterpoint to Rehberg’s programmed and sampled sounds, as though breathing malevolent life into some great, superintelligent machine. Nowhere is this effect made clearer than on the 21-minute epic “Paratrooper”, which despite its title sounds less like a crack soldier and more like a menacing, threatening beast. Guest drummer Atsuo (of Boris) weighs in with dark, claustrophobic percussion, the beats hemming in the guitar. As the drums subside the music briefly becomes lighter and more aerated, before Atsuo picks up where he left off and the whole thing descends once again into some infernal swamp.

Jim O’Rourke’s production job is suitably glacial, investing “Benbbet” and “Eternal Winter” with icy, doom-laden atmospheres. On the closing “Natural Trouble”, meanwhile, Rehberg allows his more playful side to come through, as his trademark spacey effects are for once given room to breathe amid the unusually restrained lines of O’Malley’s guitar. And given that ritual is one of the key elements of O’Malley’s work with Sunn O))), it hardly comes as a surprise when Atsuo returns on the gong, adding a ritualistic aspect to proceedings that is wholly in keeping with the sombre and devotional air of this fine record.