Ten luxuriant, often dark songs ranging from Martian electronica to inimitable balladry to id-channeling reveries, with African percussion, thick brass and deeply emotional singing: That’s Bjork’s new album in a nutshell, and, as usual, she sounds like no one but herself. Volta is arguably Bjork’s loosest and most ruminative record, and though it touches on everything she’s ever done, it’s not as gripping or coherent as her best stuff, notably 2001′s Vespertine. But with help from well-picked collaborators, including Timbaland and Malian kora player Toumani Diabate, the gratuitously detailed new disc...