Once, the new Broadway musical based on the Oscar winning Irish film of the same name, opened on this weekend to standing ovations and critical raves. CAHIR O’DOHERTY reviews the new show, which he says surpasses the original film, for The Irish Voice.

There's a reason that audiences are flocking to see Broadway shows in record numbers, even though they could probably fly to Dublin for the price of a premium seat nowadays.

That reason is theatrical magic. When it works it surpasses any drug on the market. That magic happens when you’re sitting in a darkened theater with 300 other people and an actor on the stage is breaking your heart into a million tiny shards.

I defy anyone to attend Once, the deeply affecting new musical based on the Irish film of the same name, and not be swept away by the sincerity of the performances and the music.

When these actors let loose onstage (and let me tell you they really let loose), any lingering moaning about outrageous ticket prices will be balanced by the timeless beauty of the human voice raised in song. That’s a trade-off that’s actually worth making here.

Based on the 2006 Irish film that quietly conquered all before it on its way to the Oscars (ending up with an Oscar for Best Original Song), the plot of Once could be written on a napkin -- a broken hearted boy meets a broken hearted girl who wants to help him out of a dead end. They succeed. Then they face unexpected consequences.

There’s more to it than that, of course. This is an Irish story, reconfigured by Irish playwright Enda Walsh, so it’s a script filled with jet black humor and something I have never seen in a Broadway show before, a profound and completely inconsolable sadness.

It’s not the I-loved-her-but-she-done-me-wrong sadness that we associate with musicals. It’s something far deeper and harder to bush off.  We watch two characters experience the kind of wrenching disappointment that can unmoor a life and send a soul spinning.

Irish dramatists have never been afraid to look life’s disappointments directly in the face, but I’ve never seen another Broadway musical that refused to soften the blows the way that Once does.

That gives the show’s emotional center a degree of rawness and romantic yearning that I’m warning you about right now. Once you pay the money and take your seat in the theater you’ll be on your own.

Longtime fans should note that the musical only uses the original film to supply an outline. What the actors, playwright and director have come up with -- and I don’t say this lightly -- is a much finer show.

You’ll get the first intimations of what’s ahead of you when Steve Kazee, who plays Guy, performs a song called “Leave” on a Dublin street that is overheard by the passing Girl (Cristin Milioti).

Kazee, who looks like he was factory farmed in a facility that specializes in creating leading men, begins quietly and builds, finishing the song with howls of pain and anger that seems to erupt from deep within him. It’s a staggering performance that should cement the career of the young Broadway veteran.

Guy’s been left behind, forlorn and broken-hearted, in Dublin by a girl who’s set off for a new life in New York City, which may or may not eventually include him.

On his own, and dying of it, he haunts the scenes of his former happiness until he’s confronted by Girl, a Czech immigrant who secretly sees more than a little of herself in him.

“I can’t wait forever is all that you said,” Kazee sings. “And you won't disappoint me -- I can do that myself. But I'm glad that you've come now if you don't mind, leave…” You can hear what it costs him to be left behind by the love of his life in every line he sings.

Kazee then does something I would have thought impossible. He makes the Swell Season song his own in an onstage act of reclamation that Glen Hansard and Marketa Irgolva, the stars and Oscar winning songwriters of the Once film, have admitted they were amazed by.

They’re not the only ones. Both Broadway audiences and veteran critics have been floored by the completely jarring Irish aspects of the show, which contrast strongly with typical fare.

Irish musicians simply don’t write musicals, it’s not a form they’re versed in or that they ever pursue. So the creative team behind this show had to take the mountain to Mohamed, bringing Broadway to Dublin, rather than the other way around, which could have turned Once into this year’s version of that spectacular multimillion dollar flop The Pirate Queen. It turns out that going there is better formula for a Broadway hit.

Another masterstroke was casting Milioti as the young Czech immigrant who’s simply known as Girl. With her enormous doe eyes and her tiny frame she’s a whirlwind of determination and charm, and she owns the stage from the moment she appears.

Wisely Milioti has refused to see the film on which the show is based, which has left her free to create her own characterization that fans will note differs wildly from Irglova’s performance in the film.

It’s when Milioti finally sits at her piano and begins to sing that both she and Once take flight. The surprising strength of the emotions being expressed leave no room for irony, and we watch as her character moves from an outline to a human being.

It must be said that as the show progresses, playwright Walsh’s script veers unevenly from naturalism to his trademark heightened mayhem, which does not always serve the show.  Most often the immigrants trying to make it in Celtic Tiger Dublin have their struggles played for laughs.

Will Connolly, who talents far outshine his minor role, plays a bright young Czech man who works in a burger joint but has dreams of a promotion.  Walsh has given him an outsize purple bow tie to mock his dream rather than lament its failure.

There are some absolute clunkers too when Walsh has characters talk about love and all the misfortunes it can rain upon us. Walsh, whose most famous works indicate an antic consciousness, is never really at home with this kind of sincerity, and the script suffers whenever he has no choice but to acknowledge the undeniable potency of romantic love.

Paul Whitty plays the owner of the Dublin piano store where Girl practices, and the script also has him alternating between character and caricature.

Interestingly, it’s as if Walsh can’t see these workaday men as anything more than the rough drafts he’s crafted for them. But what his script lacks in characterization it makes up for in sheer comedy.

Walsh truly excels at upsetting your expectations, and it’s in these moments that his script really finds its feet.

What’s shocking about Once, from a Broadway perspective, is that it has an inconclusive, disappointing and completely heartbreaking ending that still somehow manages send you out into the city streets elated. That’s because it reaches deeper than many musicals ever dare to and for once the payoff is immense.

Once is playing at the Bernard B. Jacobs Theatre, 242 West 45th Street. Visit oncemusical.com for information.