LA JOLLA, CALIFORNIA • • Songwriters Robert Lopez and Kristen Anderson-Lopez are rushing to catch a performance. It is just 10 days until the first preview of their new musical, Up Here, at La Jolla Playhouse and the pressure is on.

This is, after all, their first major project on the heels of the blockbuster Disney film Frozen (2013), for which they won an Academy Award for the ubiquitous anthem, Let It Go.

That Oscar sits on an unassuming shelf in the basement of their Brooklyn home, alongside their Emmys, Grammys and Lopez's Tony Awards for Avenue Q and The Book Of Mormon.

Expectations may be high for their new musical, which starts preview performances tomorrow.

Up Here was born on a slip of paper Lopez used to jot down ideas for possible musicals after he graduated from Yale in 1997.

"I thought it would be really cool to show the world the inner life of someone like me, who doesn't have a huge personality, who deals with some personal demons and is a little bit shy and awkward when you first get to know me," he said.

But for nearly a decade, it remained stashed away, while he went on to work on Avenue Q and The Book Of Mormon, and Anderson-Lopez wrote an off- Broadway musical, In Transit.

Together, they wrote new songs for the children's TV series Wonder Pets!. Then came Frozen, the Disney movie that introduced the world to sisters Elsa and Anna, to Olaf the snowman and to the Lopezes themselves.

"We loved doing Frozen," Lopez said. "But this project obviously predates Frozen and it's the most personal project that we have."

The romantic comedy revolves around an introverted computer technician named Dan (newcomer Matt Bittner) and an extroverted T-shirt designer named Lindsay (Betsy Wolfe) as they enter into a relationship constantly interrupted by competing voices inside Dan's head.

"The story is really a love triangle between a guy, a girl and his brain," Lopez explained.

It is an experiment in psychology, whimsy and, to some extent, auto- biography.

"It's this dialogue between the epic world of our feelings and thoughts and very small, mundane steps in any relationships, even just making a phone call after you've met for the first time," Anderson- Lopez explained.

"When it happens to you, it feels epic."

But while elements of Up Here were plucked from the married couple's lives and their personalities resemble those of their characters (hers ebullient, his more reflective), they insist it is not based on them.

It was not until 2007 when they met the show's director Alex Timbers that things started moving on Up Here.

By 2010, they held their first workshop performance and realised they needed a full staging to visualise the show.

It was Timbers who pitched the idea of doing the musical at La Jolla, where he had staged Peter And The Starcatcher in 2009. Nestled on a woodsy campus just outside the San Diego city limits, the theatre is far from the glare of New York, though with a track record of sending musicals to Broadway.

For the creative team, one of the challenges of the musical, which features a cast of 22 and a 10-piece orchestra, has been finding ways for the audience to visualise what is going on inside Dan's head as forces try to pull him in one direction or another. To do this, they created a world exploding with colour, playful costumes, animated projections, tap-dancing cactuses and singing miners.

The score incorporates a wealth of music influences, from Stravinsky to the Beatles and the Monkees to Sondheim and Sara Bareilles.

"There are cartoons and very intricate feelings in your head and that's sort of why you can have all these different styles in one score," Lopez said.

Once they finish on Up Here, which opens on Aug 9, they are on to their next projects, including a stage adaptation of Frozen, for which they are writing about a dozen new songs.

There will probably be a few more summer camp commitments, too.

"You hope that you can have time to do the work and listen and get enough sleep and remember to buy the baloney for the kids' sandwiches," Anderson-Lopez said. "Whether Up Here goes well or not, that's our touchstone. Life continues."

Lopez added: "For good or bad, we're going to be buying baloney."

NEW YORK TIMES