After gonzo splicings of folk and hip-hop, Mutations sees Beck trade those sample-heavy sonic tapestries for something reflective, subtle and unadorned. Not that a determinedly old-fashioned approach (the whole thing was recorded in 14 days with Radiohead’s Nigel Godrich) signals a retreat to the predictable. From grunge-sprinkled yearning (“Cold Brains”) and distorted Dylanisms (“Bottle of Blues”) to sun-fried bossa nova (“Tropicalia”), this is classicism shot through with Beck’s gift for textured, surprising songcraft.