Once: One boy, one girl, one bar, four stars

Broadway-bound is not an adjective one tends to associate with Enda Walsh. Housebound, yes. The Irish playwright's stylish tragicomedies tend to revolve around misfits unable or unwilling to leave their homes. Bedbound, too: That's even the name of one of his weirder works.

And yet, in adapting the music-filled Irish movie Once for the stage, Walsh has a Broadway-bound hit on his hands. He's fleshed out the film's proto-romance with amusing secondary characters and carved out a narrative, through folk-rock songs, that leads to an ending equal parts heartbreaking and hopeful.

I'd almost say Walsh is the key to why Once is one of the most charming new musicals of the year, but this is one of those productions that delights from just about every angle.

The 2006 movie, you may recall, was an indie hit about a Dublin busker and a Czech single mother who have a brief encounter of sorts. Falling Slowly, one of the tunes written by Glen Hansard and Marketa Irglova, ended up winning an Oscar for best original song.

For the musical, designer Bob Crowley has transformed New York Theatre Workshop into an Irish pub that is so real that you can actually go up onstage before the show and order a pint or a dram. If you are so inclined, you can also sing and dance along with the musical-instrument-playing cast during their preshow jam session of fiddle-filled folk.

Out of this fitting arena for story and song, Once eventually bubbles up. He (Steve Kazee) is busking. She (Cristin Milotti) is a passerby who stays to listen.

Director John Tiffany's production instantly grabs onto the theatrical possibilities of the scenario: When, in the initial conversation between the two, He says he makes a living fixing Hoovers, one immediately rolls across the stage into She's hand.

He and She – they didn't have names in the movie, either – both have absent partners. She's raising a child on her own, the father having returned to the Czech Republic, and their marriage is in limbo. He's broken-hearted, with a girlfriend departed for London. She encourages He to woo the ex back with his music. Together, they round up a band and record a demo.

In short, He and She make beautiful music together – and the plot hangs on whether the literal will become metaphorical. Both leads are easy to fall (quickly) for: Kazee has a strong jaw line and voice, while Miliotti has an idiosyncratic singing style and is the quirky girl of every guy's dreams.

If their encounter seems more fantastical than in the film, well, the non-naturalism is suggested by the title, which is the beginning of the beginning of a fairy tale. Tiffany, internationally famous for his stunning National Theatre of Scotland production, Black Watch, directs in a heightened style that makes He and She's story resonate at an almost mythic frequency.

Once's songs rarely move the plot forward, but Steven Hoggett provides choreography that either comments on the action or deepens character. A co-founder of Britain's Frantic Assembly theatre company who was also responsible for the military movement in Black Watch (and the musical American Idiot, too), Hoggett doesn't try to knock you off your feet Broadway-style, but gently sweeps you off them. During one song, She and other women in the cast wander around dreamily in headphones, seeming to trace the contours of the aching holes in their lives. In another, the characters yearnfully enfold themselves in one another's arms.

Bleakness sneaks in here and also in the backstories of the new and rounded-out characters – whether the music-store owner facing foreclosure or the chorus of Czech immigrants who chased the Celtic Tiger and ended up stuck serving fast-food in a slowdown.

Beautifully staged, wonderfully written and with songs well worth a second (or third) listen, Once transcends most movies-turned-musicals. It's a romance that will leave you swooning, a Before Sunset for the era of Craigslist missed connections.

Once runs at the New York Theatre Workshop, 79 E. 4th St., New York, until Jan. 15; it reopens on Broadway on Feb. 28 at the Bernard B. Jacobs Theater, 242 W. 45th St.

Once