The title of John Carney's new film Begin Again suggests a refrain of some sort, which proves apt on a number of levels. This is the writer-director's follow-up to 2006's Once, that glistening, Oscar-approved paean to music's ability to heal the heart and bring people together, and thus it might be considered the cinematic equivalent of the difficult second album: what's an artist to do after they've poured their soul into their breakthrough work, and had pretty much the whole world hear it, first in Dolby surround, then as a Broadway and West End sensation? Yet that title also describes Begin Again's faintly tricky narrative approach: how it loops back around on itself like a melody, each time accruing an extra resonance.
It begins with an English girl, Gretta (Keira Knightley), regaling the patrons of a New York bar with a sad song on the subject of what it is to be alone in the big city. The performance is, to her eyes and ears, a disaster, the song a self-fulfilling prophecy - nobody's listening - and so she resumes her place among the masses, only more convinced of her own worthlessness. A shift of perspective reveals she was, in fact, noticed: by Dan (Mark Ruffalo), a sometime music industry bigwig who shambles out of the shadows, brandishing a business card and more than half cut. Dan, it turns out, is having an even worse time of it, as his own personal flashback illustrates: usurped from the company he founded by his far steadier partner (Yasiin Bey, the artist formerly known as Mos Def), he's found himself embroiled in arguments with both his ex (Catherine Keener) and a teenage daughter (Hailee Steinfeld) who's taken her father's absence as an opportunity to veer off the rails.
Gretta returns home, understandably sceptical at Dan's offer of representation, whereupon another flashback reveals why she's clinging to sad songs: her relationship with a smoothly ambitious songwriter has just broken down, though as the latter is played by Maroon 5 frontman Adam Levine, whose ineffable dead-eyed creepiness has only been accentuated by the addition of Peter Sutcliffe-like facial hair, you would be right in thinking our girl will be better off alone. The rest of the film will comprise a fresh start, much as Once was for the lovelorn busker and yearning migrant it paired up: Dan eventually wins Gretta round to his idea of making a record independently on the avenues and backstreets of modern Manhattan, and the pair start to put the pieces, those of their hearts and those of a fragmented recording industry, back together.
For all that Begin Again constitutes an upgrade on Once - star names, American locations, more money sloshing round for wardrobe - Carney remains appreciably romantic about such endeavours. Part of this director's project with these two films is to remind us that, in an age where we can download any song ever recorded for next to nothing, there are still flesh-and-blood performers out there busting a gut, whose words and music are equally worthy of our ears and time; while this sentiment would suggest Carney has clearly never listened to, say, Kasabian or Pitbull, he's nevertheless sincere in his desire to take music out of the boardrooms and set it back down on the streets - to make poetry out of the experience of playing, and people coming together, as distinct from the market-driven connection of consumer to metadata.
It's therefore regrettable that Carney's script should be so on-the-nose in places on the matter of authenticity, not least as it immediately sets one to wondering just how authentic Begin Again really is: the fact it entails James Corden wiring up Ruffalo's Jaguar so it might function as a mobile recording studio suggests possibly not all that much. Still, though they never approach the blissful heights of Once's "Falling Slowly", the songs, penned by erstwhile New Radical Gregg Alexander, are persuasive in describing the arc whereby Gretta regains her self-belief and finds her voice, and - lest that sound overly pre-ordained - Carney is nicely relaxed about introducing them to his narrative: some hard work has gone into making them sound like the kind of thing you or I would strike up, if we had a guitar and the musical ambitions to go with it.
Rarely do you catch Begin Again straining for effect: Carney gives Knightley and Corden free rein to mess around together, thereby establishing an unforced, jamming rapport, and there's a lovely sequence that ushers the leads into Times Square with an iPod, and - without any apparent attempt to block out curious passers-by - simply sees what comes up on shuffle. The approach gives the performers space between the notes Carney wants them to hit, allowing them to better express some personality, and to nudge the film away from the more obviously formulaic areas. Ruffalo, reliably shambling, may come to define the term "hot mess" for certain viewers, yet he knows when to cede the stage to Knightley's very strong, pivotal performance: open and vulnerable whenever Gretta steps up to the mic, forthright and independent of mind away from it. Carney's second album may sound less than difficult, but it's not easy being this breezy - once, let alone twice.
Begin Again is now playing in cinemas nationwide.