Back in 2007, John Carney wrote and directed a tiny little Irish folk musical called "Once" with two no-name non-actors on a budget (about $160,000) that would have to triple itself to qualify as shoestring. What the movie lacked in funding and flash, however, it had more than enough in genuine heartwarming sweetness and tuneful soul, two commodities in short supply in Hollywood.

In a happy twist of fate, the little musical that could turned into a hit, going on to charm audiences in theaters, on DVD and at the Oscars. There, surrounded by celebrities and glitter, modest stars Marketa Irglova, Glen Hansard and his busted, rickety guitar were some of the biggest winners of night, thanks to their lovely theatrics-free performance and a speech gaff turned generous highlight (also because they literally won for Best Original Song). Even seven years later, its magical run has yet to stop, most recently evolving into a Tony-winning hit Broadway musical.

It only makes sense that, after seven years and a few projects reaching no further past his home country’s shores, Carney would want to see if the magic of "Once" could happen twice with "Begin Again." His attempt at an encore comes cleaned up of the original’s homemade, lo-fi authenticity and complete with a new starry sheen. The heart and charm are still there though.

Much like its predecessor, the little indie ditty (originally called "Can a Song Save Your Life?" -- a title both better and worse) follows two musically-inclined lost ships in the night, the ocean being New York City rather than Dublin this time.

Dan (Mark Ruffalo) is a struggling record label exec, failing to find any new talent and drinking his way out of his own company. His family life with his disgruntled wife (Catherine Keener) and daughter (Hailee Steinfeld, basically still in costume from playing the same character in "3 Days to Kill") is predictably no less stable.

Meanwhile, heartbroken singer-songwriter Greta (Keira Knightley) is tending to her emotional wounds after getting left behind by her long-time sweetheart, songwriting partner and now growing superstar Dave (Adam Levine of Maroon 5), first creatively and then romantically soon after.

The two hobbled vessels – one stumbling drunk, the other distraught and bitter – cross paths at an open mic night, where Dan is entranced by the potential of Greta’s music. After some convincing and a bit of confessing, he gets Greta to try out for his increasingly impatient business partner (Mos Def).

Met with general apathy, the damaged duo dreams up a new strategy: recording an album live across the city with a ragtag band of musicians. While the album comes together, Dave and Greta’s relationship grows into something right in the middle of romance and friendship, setting each other’s broken bones and hearts and getting each other back on their feet with the healing power of music.

If that synopsis sounds a good bit like "Once," that’s because it plays a good bit like "Once." The formula is all there in place – even down to the moment where a character regretfully watches home video footage to a mournful tune – but the end result feels a bit like a good, respectable cover of a great track.

The raw yet delicate authenticity of Carney’s hit feels more like feigned authenticity here, the grit, reality and sense of melancholy replaced by sweet if naïve commentary about the cold music industry, familiar story elements – like Dan’s home and record label woes – and some forced eclectic "character." There’s just enough Hollywood formula and polish to deceive the film’s ragtag underdog spirit. It’s the difference between an old dinged up rustic homemade desk and one whose dings and marks came premade.

The music, however, might be the biggest letdown. It’s not that the tunes, written by former New Radicals frontman Gregg Alexander, are bad. They’re just very typical singer-songwriter tunes, lacking much personality or power. There’s no "Falling Slowly" or "When Your Mind’s Made Up" (sorry for all the "Once" comparisons, but it’s hard when "Begin Again" echoes it so closely) among the bunch. They’re nice but anonymous, and as much as the film tries to convince the audience of the potential hits on the leads’ hands, it’s hard not to do one’s best impression of F. Murray Abraham in "Inside Llewyn Davis" and say, "I don’t see a lot of money here."

What "Begin Again" lacks in hits, however, it makes up for in heart. Even if the songs aren’t exactly prime earworms, Carney sells them with a heartwarming sweetness. Knightley’s first song at the open mic night, for instance, isn’t a great track, but the way Carney presents the song playing and assembling in Ruffalo’s mind – with inanimate background instruments coming to life and joining in – is pretty beautiful and fittingly imaginative.

None of the other songs gets that treatment, but thanks to his character work and emotional sincerity, they may not lift your soul, but they’re performed well enough to lift the corners of your smile.

He’s even better with the main relationship between Dan and Greta, establishing and developing it at a pleasantly laidback, relaxed pace. It helps that the actors at his disposal are better than the songs. Ruffalo is his predictably soulful self, while Keener, as is her specialty, seemingly brings a whole life lived on screen with her, even to the smallest parts. Brit actor James Corden gets to steal a few scenes as well as Greta’s sweetly loyal flatmate.

The real star of the show is Knightley. Usually stuck in chilly prestige roles, the actress is freed from her usual period piece costumes and corsets and ends up delivering one of her most easy, charming performances. Her voice is a touch whispy (she makes Irglova’s fluttery voice sound damn near operatic), but her sweet, surprisingly snappy performance – and the chemistry she strikes up with Ruffalo – makes up for it.

They say lightning doesn’t strike the same spot twice. Even with its substantial charms, "Begin Again" technically proves that, but Carney and company hit close enough that one can at least feel the soul-tingling static.