Critics, voters and audiences all agree that Once has brought something special to Broadway. Since its first workshop less than two years ago, Once has won eight Tony Awards®, including Best Musical, captivated thousands of people a week at the Bernard B. Jacobs Theatre and become the unlikeliest smash hit on Broadway.

To some degree, Once was following the template set by the 2006 film of the same name. Shot for less than $200,000, the romantic drama depicted the bond forged between an Irish street musician (Glen Hansard) and a Czech immigrant (Markéta Irglová) in Dublin over their shared love of music.

In addition to becoming a sleeper success, the film generated enormous attention for its soundtrack, which was written by Hansard and Irglová. One song, the duet “Falling Slowly,” would win an Academy Award.

When the producers called director John Tiffany to propose turning the film into a musical, that Academy Award performance was his only exposure to Once. But he downloaded the soundtrack that night and fell in love with it.

“What drew me to Once was the music,” he says. “It’s that simple. It’s written from the heart. It tells a truthful story.”

Robert Cole, the musical’s executive producer, echoes Tiffany’s comments almost exactly. “In my opinion, it’s the best score on Broadway,” he says. “It’s of the heart, and so it has a more profound emotional effect than your average musical.”

Tiffany quickly signed on and brought the choreographer Steven Hoggett with him. The two have worked on several hard-edged projects together, notably the acclaimed Iraq war drama Black Watch. However, they quickly realized that the gentle, folk-tinged tone of Once would require a very different vocabulary.

But not the standard Broadway-musical vocabulary. “I would have destroyed Once had I turned it into a song-and-dance show,” Hoggett says. “It’s crucial that these characters seem like utterly normal people.”

Upon seeing the film, Tiffany quickly seized upon a party scene in which the characters stand up and burst into raucous song. His own father was an amateur musician who would bring him to similar settings as a young man. Suddenly, he says, “I saw an ‘in’ as to how we can turn it into a piece of theater. That idea of having everyone singing their song and having their turn appealed to me.”

His brainstorm was to turn the entire stage into a festive bar, one where everyone can participate in the musical performances. And so the 12 actors, including Steve Kazee (guitar) and Cristin Milioti (piano) in the roles created by Hansard and Irglová, also serve as the orchestra. Sometimes they play on the periphery, and sometimes – as in the stirring ballad “Gold,” which Hoggett says “caused a lot of brain meltdowns” in rehearsal – they spin, stomp and kick their way across the stage while still playing.

This brought its own complications, but Tiffany says that “after that initial bit of shock, the cast really embraced it.”

Steve Kazee, whose performance as the soulful, haunted Guy earned Once one of its eight Tonys, says he can’t imagine the show being performed by the usual pit orchestra. “It’s a show about a guy, a girl and a band,” he says. “I don’t know how you can do it otherwise.”

Kazee remembers joining Hansard at an Irish pub during rehearsals. “We sat in a circle and just traded songs,” he said. “It’s a very shared environment, and we tried to replicate that on the stage.”

After the Cambridge workshop, which culminated in 10 public performances, Once moved to an off-Broadway run at New York Theatre Workshop in the East Village. The audience response was rapturous, and Cole spearheaded the move to find a Broadway theater that could ultimately house the show.

The moment the Jacobs was secured, the producers made the extremely rare decision to announce the Broadway transfer the day it opened, “much to the consternation of the critics,” jokes Tiffany. (The strength of the reviews often plays a role in deciding which shows transfer.)

With each move, the question has arisen of whether Once would still maintain its intimate, fragile charms under a bigger spotlight, where audiences are more used to spectacle. But Hoggett says they fought that temptation each step of the way. “The version that sits on Broadway is exactly what we put together in Cambridge,” he says. “There’s no extra feet kicking in the back.”

Cole, who maintains that Once is more intimate at the 1,100-seat Jacobs than at New York Theatre Workshop, praises the creators as well as his fellow producers for handling the transfer “with care and with a strong belief that we were not compromising our standards.

“They knew what they were doing,” he says of the creative team, “and as producers, you have to trust that.”

Kazee agrees: “We found that as long as we were honest about what we were doing and didn’t buy into that mentality, people kept responding. We really haven’t changed a thing, and I hear silences up there that I’ve never experienced before as an actor.”

One rather unusual aspect of Once, one that hardly lends itself to silence, occurs before the show begins. The actor-musicians meander onto the stage and launch into a seemingly impromptu concert, one that audience members can drift up and join.

Tiffany believes this jam session sets a tone that he and the rest of the Once team has worked hard to maintain. “It becomes a dialogue in a way,” he says. “Maybe they leave a little bit of themselves up there when they go back to their seats.”

By John Allendale