There’s something deliciously perverse in hearing Justin Timberlake sing – gorgeously, it must be said – old-timey roots music. He’s a minor character in the Coen brothers’ rich Sixties-folk-revival tale, and also on this handsomely lean soundtrack, sung mostly by the fi lm’s cast. His colleagues do fine, notably star Oscar Isaac (see the sweetly grim English ballad “The Death of Queen Jane”) and Girls guy Adam Driver (singing bass “uh-oh!”s on the fauxperiod novelty “Please Mr. Kennedy”). But off screen, only the group harmonies – “Five Hundred Miles,” with Timberlake and co-star Carey Mulligan; “The Auld Triangle,” with Marcus Mumford and Timberlake – head toward the sort of spine-tingling that defined the soundtrack to the Coens’ O Brother, Where Art Thou? That LP’s producer, T Bone Burnett, is on board here, and the Punch Brothers add low-key accompaniment. But none of the actors have the vocal character of the late Dave Van Ronk, whose biography inspired the film and whose bluesy “Green, Green Rocky Road” caps this set, or of another folk singer – the young Bob Dylan – whose rarity “Farewell” signals a new era dawning in the film and on this collection. Now, as then, he’s the yardstick.