If you read the brief summary of In Transit on its official website, the show “follows the intertwining lives of eleven New Yorkers, all hoping to catch the express train to success, love and happiness—and the stops they make along the way.” It sounds like the typical make-it-in-New York story, but after talking to Kristen Anderson-Lopez (one member of In Transit’s four-person writing team) it’s due to be so much more.

Anderson-Lopez, who may be best known for co-writing the score for Frozen with her husband, Robert Lopez, joins with three of her close friends to bring their musical to Broadway’s Circle in the Square this fall. In fact, Anderson-Lopez, James-Allen Ford, Russ Kaplan and Sara Wordsworth just returned from a retreat at the Eugene O’Neill Theater Center, where they worked for nearly 54 hours straight, revamping and rewriting the musical that took shape on the O’Neill campus in 2008.

READ GO BACK TO WHERE IT ALL BEGAN FOR ROBERT LOPEZ AND KRISTEN ANDERSON-LOPEZ

“We really found our story at the O’Neill in 2008,” says Anderson-Lopez. “The DNA of what the show is was found there, but that’s maybe 20 percent of what still exists.”

The show is certainly a love letter to New York. In fact, that’s why director Kathleen Marshall signed on. “She said, ‘It’s the Wonderful Town of today,’” says Anderson-Lopez. That’s due to the fact that the story is inspired by the four writers’ own experiences trying to find their place in New York City—particularly as artists.

“There’s a song in In Transit called ‘Do What I Do,’ which is about how when you’re trying to become an artist, the question of what you do is so complicated because you’re usually doing one thing for money and one thing for love,” says Anderson-Lopez.

But even if you’re not a struggling artist, there is something incredibly relatable in In Transit’s story for today’s lightning-speed, tech-distracted, achievement-oriented generation. “All of us realized: Many falls always came from being so focused on getting somewhere that we were never breathing and opening our eyes where we were and enjoying the fact of being young in New York,” says Anderson-Lopez. “The subway is an incredible metaphor for the way that we, as New Yorkers, are always trying to get somewhere, but are never satisfied with where we are.”

The idea for the show to be an a cappella musical, not a revue, was there from the start. “James-Allen Ford and I went to the BMI Workshop [together],” says Anderson-Lopez. “We were assigned to each other for our ten-minute musical, and we thought, ‘You know what? How can we use a cappella and everything we learned through BMI about writing musicals, writing stories through song, and combine them?”

Of course, getting an a cappella musical off the ground is a difficult task. There’s a reason why it’s never been done before. “You can’t shop this around town because it takes a lot of voices coming together,” explains Anderson-Lopez. “Equity has 29-hour readings, but we have 300 pages of score, so every reading, you can’t just cast it lightly.”

“It’s like a five-dimensional Rubik’s cube,” she says. (Pitch Perfect’s Deke Sharon is putting together the arrangements for the production.) “[The actors] have to be incredible musicians, and on top of that, they all have to fit the puzzles of their vocal genius with each other. It’s actually an incredibly trick thing to put together, but…when it does come together in the right way, it’s something unlike anything you can experience.”

And that may be because, as Anderson-Lopez reveals, “at the center of [the show] is one of the best beat boxers in the world.” The beat boxer is the “heartbeat at the center of our show,” and with wins at national beat-boxing conventions, he’ll be a sound worth hearing.

A cappella isn’t just the vehicle through which the story is told, it’s also a larger metaphor of In Transit. “If you think of New York as a vocal ensemble, we all think we’re singing the solo of our [life], but we’re in fact the backup to everyone else in New York, right?” says Anderson-Lopez. “And everyone else in New York is the backup to our solo. There’s this incredible harmony and music in New York, and if you stop and listen, you realize you’re a part of it. That’s why it’s a cappella.”

And just like the next train, we can’t wait for it to arrive.