This documentary on a musical hangover arrives some time after the facts. It is (somewhat astonishingly) five years since Glen Hansard and Markéta Irglová won the best original song Oscar for their work on John Carney's Once. Shortly after that success, touring under the name The Swell Season, the duo underwent a difficult professional and romantic breakup.

Wisely or not, Hansard commissioned three directors to film what ended up being a sad story. Irglová is not happy with the nature of modern fame: fans lurking at every stage door with camera phones; exhausting hikes from one anonymous venue to the next. Tensions between the performers bubble to the surface. An inevitable dissolution looms.

The Swell Season is a peculiar beast. Once was not originally written for Hansard and Irglová, but it plays awfully like their story: Dublin man and Czech woman unite over music. So, the documentary – elegantly shot in black and white – can't help but come across as a sort of accidental sequel. The odd, slightly off-key ending to the saga is all on camera: every relevant conversation seems has been captured in bizarrely intimate close-up.

Along the way, we get some borderline-hagiographic insights into the steady rise of Glen Hansard. His troubled dad and indomitable mother speak movingly of their pride in his success. Clichés of the rock documentary do make occasional appearances. The Frames frontman should, by now, be aware of a golden rule for any such production: study Spinal Tap and don’t do anything they do.

To be fair, Hansard’s pronouncements on life and music stay just the right side of pomposity. But the decision (recalling Tap’s Derek Smalls) to pull out a pipe is seriously misguided. The only people under the age of 60 who now look comfortable with such items are gamekeepers and fisherfolk. You, sir, are neither.