Idina Menzel and company in “If/Then.” (Joan Marcus)

Usually, talking during a performance is strictly a no-no. But in the final days last fall of the Washington tryout of their new musical “If/Then,” Brian Yorkey and Tom Kitt couldn’t resist. By themselves in box seats in the National Theatre, they would watch the show and whisper ideas back and forth about what needed fixing as they contemplated the musical’s opening night on Broadway a few months hence on March 30.

Those sotto voce discussions launched what they and others in the show’s inner creative circle describe as a significant retooling of the $10 million production, which stars Idina Menzel as a woman at a midlife crossroads, who is given two possible futures. In the weeks that followed, composer Kitt and lyricist and book writer Yorkey, along with director Michael Greif and producer David Stone, embarked on a process of figuring out what to remove or add, reshape or replace, to develop what they hoped would be an “If/Then” with more clarity and emotional texture.

As a result, they say, the “If/Then” that has just started preview performances at the Richard Rodgers Theatre is a musical containing some new material in practically every scene, and several scenes have bigger changes. Three songs from the National Theatre production have been cut, they report, and two new songs — written since D.C. — have been put in. Another number has been “relocated” in the story, and yet another has been, as Stone said, “dramatically repurposed.”

And the musical will also be shorter. Running two hours and 50 minutes at the National, “If/Then” has been trimmed for New York by 12 minutes, the producer said. “Twelve minutes?” Greif asked Stone a bit nervously, as the creative team gathered at the Rodgers one recent afternoon to talk about the changes. “You have to consider breaks for applause. Are you sure we want to — ?”

Stone held his ground. “Yup, 12 minutes shorter.”

“If/Then” is Kitt and Yorkey’s Broadway follow-up to “Next to Normal,” the musical about a family coping with mental illness, also directed by Greif and produced by Stone, that won the 2010 Pulitzer Prize for drama. The new show, which also features “Rent” veteran Anthony Rapp and LaChanze, a Tony winner for “The Color Purple,” is conceptually tricky, a fact borne out in the world-premiere D.C. run that ended Dec. 8. The musical’s “what if?” format supposes that Menzel’s Elizabeth arrives in New York on the cusp of 40 and, faced with the complexities of career and relationship choices, takes her into two competing realities, one as Liz, the other as Beth.

As some reviewers and audience members noted in Washington, the details of the divergent plots — even that there were divergent plots — were not always as apparent to theatergoers as the people behind “If/Then” imagined. Deficiencies in choreography and the weakness of some of the songs, particularly in the long first act, were also widely talked about in reviews and online commentary. While all of these elements have been — and are being — addressed in the run-up to opening night, refining the narrative so that the separate paths are better defined has been paramount.

“There wasn’t a lot of confusion about what we needed to look at,” Stone said, adding that the D.C. tryout met his expectations for the time-honored value of taking a big, complicated musical first to a city outside of New York with a sophisticated audience. “What an out-of-town tryout does is it teaches us what our show is.”

And, in fact, the team received a lesson. “We were asking the audience to make a lot of pivots,” Yorkey said. “And we found some exciting ways to clarify that and to make things concise.”

A lot of what Washington audiences saw will be recognizable in the Broadway incarnation, according to “If/Then’s” creators. (Critics are not invited to see the show until March 27, and reviews will run on March 31.) The cast, for example, is exactly as it was, and the majority of the numbers remain intact. While the songwriters, director and producer wouldn’t reveal which songs were cut, they did say that the opening number has been reconceived in hopes the idea is better established that Elizabeth sets off on one journey and then rewinds and goes off on the other path. More indicators have been added, in terms of visual cues as well as the situating of secondary characters, to anchor the audience in either the Beth or the Liz stories.

Greif said, too, that for a spell, he and choreographer Larry Keigwin worked with his dance company, Keigwin + Company, to flesh out “If/Then’s” dance sequences. “To have those weeks free of pressure really helped us,” the director said.

There’s only one way to tell, though, whether all the extra work has enhanced “If/Then.” As Yorkey observed: “Most of the people who come to the Rodgers don’t know how far we’ve come. They only care if there is a well-told story.”