Your reaction to a duet between Joan Baez and Marcus Mumford will determine your enjoyment of this concert movie, which represents either a passing-of-the-flame folk moment or hipster culture's appropriation of all that is sacred. It's a similar exercise to the Coens' O Brother, Where Art Thou? soundtrack, marshalling musicians young and old, including Jack White, Gillian Welch, Patti Smith and Oscar Isaac – Llewyn Davis himself – for a night of close harmonies, virtuoso plucking and mock-Irish balladry. Rehearsal and backstage footage add variety, and there's a warming egalitarian camaraderie to the venture, though sadly no room for the movie's novelty space song, Please Mr Kennedy.