Begin Again, film review: Keira Knightley is on song for John Carney's fairy tale of New York

Keira Knightley plays Greta, a Norah Jones-like singer-songwriter in John Carney's Begin Again, formerly known as Can a Song Save Your Life? It's a typically brave performance from an actress who is always prepared to try anything. Mark Ruffalo is Dan, a record-company exec whose life is in meltdown but who recognises Greta's potential after hearing her perform in a tiny New York club.

The film's attitude toward the music business is nothing if not contradictory. Carney, who enjoyed a huge hit with his low-budget, similarly themed Once, seems to be on the side of street musicians who write songs for the love of it. Greta's boyfriend (Adam Levine) is portrayed in a negative light for pursuing fame at the expense of artistic integrity.

Nonetheless, as viewers, we are always aware that this is a star-driven romantic comedy. The film suffers from its own relentless optimism. There's no darkness or sense of suffering here. Ruffalo is a brilliant character actor who, at times, plays Dan as if he's on leave from a John Cassavetes drama. Carney, though, blithely glides over Dan's alcoholism, faltering career and family trouble.

There's little desperation about Knightley's character, either. She's a well-spoken young English woman who can go back to "uni" if her adventures in the music business don't come off. With so little at stake, it is no surprise that the songs themselves, though perfectly capably performed by Knightley, are on the vapid side.