If something works “Once,” do it again, only bigger. That seems to be the idea John Carney’s embraced with “Begin Again” (formerly titled “Can A Song Save Your Life?”), which—like his surprise-smash micro-budget 2007 charmer that also spawned a hit Broadway show—emphasizes the power of music to repair real-life personal damage. Lightning may not strike the second time to quite the same degree, but thanks to the performances and the tunes, you’re likely to find yourself willing to go along with the message again, as the title suggests.

Dan (Mark Ruffalo) and Greta (Keira Knightley) meet when both are at a low point. He’s an old-line, down-on-his-luck music producer divorced from his wife Miriam (Catherine Keener) sand estranged from his daughter Violet (Hailee Steinfeld); rumpled and boozy, he’s also just been fired by his businesslike partner (Yasiin Bey, otherwise known as Mos Def), and is contemplating suicide. Stumbling into a bar, he encounters Greta, who’s just been coaxed by old her pal from England, street busker Steve (James Corden), to get up on stage during open mic night to sing one of her songs. She’s gloomy too, having just broken up with her long-time boyfriend (and collaborator) Dave (Adam Levine), who’s hit it big as a singer and linked up with one of his label’s pretty execs.

Though presented in pretty linear form here, Dan and Greta’s back stories are shown in more imaginative juxtaposition by Carney, who shifts back and forth between them, repeating moments as needed, to draw us in. Equally clever is the way in which he depicts the special fashion in which Dan hears Greta’s song. While the rest of the audience is dismissive or bored, he’s enraptured by what he discerns as an extraordinary talent, and though Greta is singing while strumming a guitar, he visualizes how she would sound with instrumental backup. It’s the moment in so many musicals when suddenly an unseen orchestra intrudes during a number that begins as a solo, here transformed by Carney into something visually magical by introducing each instrument playing on its own.

From this point the film’s trajectory is predictable, with Dan offering to oversee the making of a demo album for Greta and her encouraging him to reconnect with his wife and daughter in the course of the project, which he conceives as being recorded on site in various NYC locations. It’s frankly an unbelievable premise, since ambient noise in the city would make that sort of operation pretty much impossible. But it nonetheless makes for some amusing scenes of the group performing without benefit of official sanction, as well as a couple featuring Cee Lo Green as a rapper who owes his success to Dan and is happy to help out his old producer now.

Still, the major focus is on the development of the relationship between Dan and Greta, which isn’t exactly businesslike—the two share long walks and conversations about their favorite music—but at the same time avoids slipping into romance. For each of them, fulfillment lies not in falling in love with one another, but in achieving their musical dreams, his involving producing an album that he can actually believe in again, and hers making the music she creates available to other ears. The give-and-take is expertly played by the stars, with the shaggy Ruffalo bringing a Tracy-like gruffness to the driven Dan and Knightly some of Hepburn’s prickliness to Greta. Corden registers strongly as the ebullient busker, and both Bey and Green slyly spoof their characters, while indie stalwart Keener and young Steinfeld are fine as Dan’s family. And Levine is surprisingly effective as the sudden star who seems at a loss about how to handle new newfound fame.

Cinematographer Yaron Orbach takes the myriad opportunities afforded by Carney’s script to revel in the byways of the Big Apple, but the most important non-acting aspect of “Begin Again” is certainly the music, and the new songs—mostly by Gregg Alexander—are likable, even if they don’t match those that Glen Hansard and Marketa Irglova penned for “Once.” Curiously, for a story that emphasizes unconventionality (including, as a topper, a decision about how to sell Greta’s album), a scene in which she and Dan trade their playlists offers tunes that come across like remarkably safe—even humdrum—choices.

On balance, however, “Begin Again” provides another nice musical spin by Carney on the conventions of quasi-romantic dramedy.