Though Christopher Ashley is departing for New York in December, one might say he’s leaving his “Heart” in La Jolla.

Following four weeks of rehearsals, script adjustments and additional research of its subject matter, Ashley will lead the world-premiere musical “The Heart” to the stage at La Jolla Playhouse beginning Tuesday, Aug. 19. After a week-long series of previews, the production will continue through Sunday, Sept. 28.

It’s the next-to-last show Ashley will direct as the playhouse’s artistic director before he leaves to lead New York’s Roundabout Theatre Company.

“The Heart,” based on the French novel “Réparer les Vivants” by Maylis de Kerangal, is set in San Diego over the span of 24 hours as it follows a late young surfer’s donated heart through its journey to a critically ill recipient.

The playhouse describes it as “an enlightening, edge-of-your-seat ride.”

Unlike revivals of musicals such as “Cabaret” and “Camelot,” in which the script and score are set before production, “The Heart” is new, with a book by Kait Kerrigan, who also contributed lyrics, music and lyrics by Anne and Ian Eisendrath and choreography by Mandy Moore.

As such, Ashley guesses every page of the script has been modified in some way over the past four weeks, and the team has thrown out two songs and wrote two originals in their place.

“This is the first time it’s ever been done, so it’s being rewritten as we’re working on it,” Ashley said. “It’s kind of like flying a plane while you’re building it.”

Part of that process included research that Ashley said enabled the cast and crew to be immersed in the spaces where the story takes place.

“Because half of it happens in hospitals, we’ve had amazing conversations with all kinds of top-notch medical personnel about what they do and how it works — people who work in transplants, people who do cardiovascular surgery and all the amazing people who work in emergency rooms around the city,” Ashley said.

The creative team behind "The Heart" consists of (from left) choreographer Mandy Moore, songwriter Anne Eisendrath, book writer Kait Kerrigan, songwriter Ian Eisendrath and director Christopher Ashley. (Tia Byington)The creative team behind “The Heart” consists of (from left) choreographer Mandy Moore, songwriter Anne Eisendrath, book writer Kait Kerrigan, songwriter Ian Eisendrath and director Christopher Ashley. (Tia Byington)

And that isn’t all.

“It also starts with a surfer catching the first wave of the morning,” Ashley said. “So all the cast has been learning to surf, if they already didn’t know how.”

One of the key elements propelling “The Heart” is a musical score that Ashley describes as very different from his past experience as a director.

“The EDM [electronic dance music] vibe of the score uses the sounds of hospitals, of nightclubs, of the beach and the ocean and of the human heart,” he said. “So it’s this very unconventional kind of innovative set of sounds that come together to make the score.”

The show sports a cast of nine actors who embody more than 40 characters. Many of them are familiar faces at La Jolla Playhouse, including Heidi Blickenstaff, who starred in “Freaky Friday,” Zachary Noah Piser of “Redwood” and Paul Alexander Nolan (“Escape to Margaritaville”).

Ashley says “The Heart” comes at an especially relevant time.

“It’s very much a story about what we owe our fellow human beings, even those we may never meet,” he said. “And it feels like a great time in history to tell a story about generosity and about taking care of each other.

“We’re living in such a fractured moment that it’s great to tell a story that ultimately makes the case for how interconnected we all are.”

La Jolla Playhouse Artistic Director Christopher Ashley (right) speaks with cast member Lincoln Clauss during a rehearsal for the world-premiere musical "The Heart." (Samantha Laurent)La Jolla Playhouse Artistic Director Christopher Ashley (right) speaks with cast member Lincoln Clauss during a rehearsal for the world-premiere musical “The Heart.” (Samantha Laurent)

Ashley will cap his 18 seasons at the playhouse by directing an adaptation of “Working Girl,” the 1988 film starring Melanie Griffith, Sigourney Weaver and Harrison Ford. It is scheduled to open in late October.

And even as he prepares for the debut of “The Heart,” he’s already at work on his next project.

“In the mornings, while we’re teching ‘The Heart,’ I’m back on Zoom and on the phone finishing up casting for ‘Working Girl,’” Ashley said. “It’s always a juggling experience directing in American theater.”

‘The Heart’

When: Aug. 19 through Sept. 28. Show times are 7:30 p.m. Tuesdays through Fridays, 2 and 8 p.m. Saturdays and 1 and 7 p.m. Sundays (8 p.m. only on Saturday, Aug. 23).

Where: Sheila and Hughes Potiker Theatre, La Jolla Playhouse, 2910 La Jolla Village Drive

Cost: $30-$119

Information: lajollaplayhouse.org/show/the-heart ♦