Listening to the Norwegian power-trio's take on Sonny Sharrock's ‘As We Used To Sing,’ which opens their fourth album, is a little like taking a bath in raw, musical endorphins. The joy and heart-bursting exuberance are almost palpable as they take Sharrock's soaring riff for a run, with guitarist Hermansen rolling out chorus after chorus and revelling in glorious post-Hendrix overdrive that combines jazz inventiveness with crunching attack. It's a sound that imagines a universe where blues-derived early-1970s hard rock failed to flatten out into metal, and improvisational flair remained the key. Elsewhere, there's driving funk-rock; a slow, stoner-twang that picks up on Earth's scorched prairie blues; and some monstrous modal rock gallop – all served up with luxuriant, analogue warmth. Seriously, if you're ever in an aeroplane, nose-diving towards certain doom yet feeling a strange, clear exhilaration at the prospect, this is exactly what you want playing on your iPod.