On the streets of Dublin, a guitar-wielding singer/songwriter (Glen Hansard, lead singer of The Frames) is just trying to make a living, belting out favorites for the passers-by. But at night, he performs powerful songs of his own, tearing open his own broken heart for anyone who will listen.

In the opening scene of John Carney’s film Once, that’s exactly what this singer is doing — singing as if his life depends on it. It takes about 30 seconds, and the audience is riveted by his intensity and passion. And a couple of minutes later, the singer finds himself in an unexpectedly hilarious chase to recover the tools of his trade.

It’s one of the fundamental rules of great storytelling — make us care about, and like, your main character, rough edges and all. And Carney does that effortlessly. This engaging, down-on-his-luck performer, whose name is never revealed, and who happens to have a day job as a vacuum-cleaner repairman, is not likely to make it big anytime soon. But no matter… he’s wins our hearts, and we’ll follow him anyway.

Against all odds, it happens again a few minutes later.

Enter “the Girl” (Markéta Irglová, a Czech actress who should have no trouble finding roles elsewhere). She’s a spirited young lass who happens upon “the Guy” during one of his curbside performances. She likes his style, and has something of her own to add to the musical mix.

And who would have guessed? She’s got a broken vacuum cleaner… and he repairs them!

Date movies don’t get more romantic and inspiring than Once. It’s an unsentimental story of new love, creative collaboration, and tough reality-checks. As “Guy” and “Girl” — we never learn their names — strike sparks that rise into fiery emo-rock performances, we’re rooting for them all the way. Will they make a hit record? Will they break loose from their troubling past relationships and run away together?

In scenes so naturalistic that they seem more real than “reality TV,” we’re drawn into jam sessions, late-night heart-to-heart conversations, family dinners, studio recording sessions, and lonely nights while the lovebirds wonder where this is all going to lead.

Whatever you think of the conclusion, you’ll be recommending this simple, near-perfect little gem to all of your friends, whether they like musicals or not. Once steers clear of the stagy spectacle we associate with big screen musicals — you’ll never hear this movie compared to Hairspray — and goes straight for the heart with subtlety and realism. The songs have contagious melodies, and although a couple of them are overused by the end of the movie, the singers convince us that they’re being sung, yes, from the heart… but also from personal histories.

And those histories have something to offer. This isn’t a love story about hormones and frivolous misunderstandings. It’s about being real, sharp edges and all, and finding someone who will listen and understand that. It’s about bonding through honesty and trust. And it is bold enough to suggest that art can be the language through which we see each other best.

After it’s over, you’ll have a hard time shaking off the notion that Guy and Girl are still out there, somewhere, jamming up a storm.

And by the end of the year, Once will be the movie doomed to lose at the Oscars but destined to live on in everyone’s hearts.