From the director of heartfelt sleeper hit Once, comes Begin Again, a charming musical fairytale of New York, starring Keira Knightley and Mark Ruffalo.

Knightley plays Gretta, a brooding English singer-songwriter who arrives in New York City with a boyfriend and a large dose of naïve optimism in tow. But when we first meet her, she has become almost completely disillusioned with music, love and the city itself. Enter dishevelled ex-record executive, Dan (Ruffalo), who has lost his job, his family and his faith in anything except alcohol. The pair embark upon an unlikely musical partnership and, along with a (literal) band of misfits, they record Gretta’s album in scattered locations across New York and fix each other along the way.

Director John Carney explores a similar sentiment to his previous venture, Once, only the A-list cast and glitzy production used this time around means he is unable to replicate the tale of the underdog quite so naturally. The central concept of the healing power of music may be a little saccharine for some, but Begin Again is nothing if not earnestly endearing, and its occasional clichés are strengths rather than weaknesses. It effortlessly avoids the cheesy stereotypes associated with movie musicals and whilst the soundtrack is lacking a breakout song like Once’s Falling Slowly, it still has merit outside of the film itself and is a thoroughly enjoyable blend of folk and easy listening.

It would be disingenuous to say that Begin Again is a textbook romantic comedy however, as Carney does create an unconventional narrative with its three interwoven stories all meeting at the same moment. But because the story is by no means indicative of the actual music industry, and nothing ever feels in jeopardy, it falls short in terms of emotional exploration.

Much of Begin Again’s success hinges upon its inspired casting; in particular, Mark Ruffalo, who is one of the few actors who could successfully endear the obnoxious Dan to the audience. Keira Knightley’s soulful Gretta is his perfect counterpart and not only is her singing voice a pleasant surprise, she also has a down-to-earth quality that is refreshing to see.

Meanwhile, Maroon 5’s Adam Levine, as Gretta’s sell-out ex-boyfriend, is tedious and uninspired, and in terms of acting merit, he joins Madonna and Britney Spears on the list of musicians who probably should have stuck to their day jobs. Similarly, the chemistry between Levine and Knightley is so non-existent that Gretta’s story suffers as a result. But the remainder of the secondary cast is remarkably strong, with rising star, Hailee Steinfeld, doing particularly well in the role of Dan’s apathetic teenage daughter.

James Corden, as Gretta’s loveable sidekick, is also an enjoyable addition, and the delightfully British rapport between himself and Knightley is easily the most genuine of the film. But it is the unconventional nature of the central relationship that provides something a little special. Although there are occasional romantic hints between Gretta and Dan as the pair revels in each other’s melancholy, it is unclear whether you actually want the two lost souls to become anything more. But a particular vignette, in which Ruffalo and Knightley stroll through New York sharing a pair of iPod headphones, is a delightfully endearing idea that provides one of the film’s goose-bump moments.

For those looking to be easily charmed this summer, Begin Again delivers in spades. A heartfelt indie flick where music and the city are as much a part of the fabric of the film as the acting itself, it is guaranteed to put a smile on your face.