The music in James Joyce

“Chikka chu, chikka chu, chikka chu.”

A trio of actors repeats the line over and over, picking up the pace and then letting it lag, raising the volume and then lowering it.

They’re mimicking the sounds of a train as it departs Paris, carrying the great Irish writer James Joyce and his wife, Nora Barnacle. And right now, the “chikka chus” are the subject of intense discussion.

How long should they go on? At what speed? What volume?

The unison “chikka chus” occur at a pivotal point in the new musical “Himself and Nora,” opening Thursday at the Old Globe Theatre. As the title characters ride the train away from the invading Germans during World War II, the script approaches its climax. The train effects introduce a summing-up song from Nora.

“They have to come out of the rhythm as soon as we hear the chord” that introduces Nora’s song, composer Jonathan Brielle tells the directors and cast. “Otherwise we’ll have a train wreck.”

Hovering around an upright piano, two co-directors and a musical director weigh in. Director Joseph Hardy notes that the authentic “chikka chu” speed is hard to determine “because there aren’t any steam engines anymore.”

Yet maybe that attention to detail isn’t terribly important. After all, Hardy notes, “Himself and Nora” is no documentary. Although it covers highlights of Joyce’s life, from his birth to his wake, “it’s not about biography. It’s an imagined, impressionistic picture of the love” between the title characters.

Still, the historical accuracy of another line in the same scene provokes some good-natured ribbing of the writer of the script, Sheila Walsh. The day before, Hardy had asked for a few new, narrated lines to provide specific benchmarks of Europe’s rush toward World War II. He suggested that Walsh write something about “Hitler’s panzer divisions” approaching Paris.

Walsh -- admittedly “not a history buff” -- returned the next day with: “As Hitler’s Pansy Division nears Paris, people flee the city.”

Soon after the new draft of the scene is distributed to the cast of five, the wisecracks begin. Walsh smiles gamely.

“Himself and Nora” was originally Walsh’s baby. When she was young, her Irish-born grandmother told her, “You don’t want to read Joyce. He wrote a dirty book.” That virtually guaranteed that Walsh would read it. “I fell in love with this man who wrote about Molly Bloom in that way,” she says.

As a struggling young actress three decades ago, she worked with Molly’s famous monologue, though never performed it publicly. She sometimes felt that Joyce was her “spiritual father,” she says.

About a dozen years ago, she began writing a play about Joyce, originally for 13 actors -- until she realized that a cast that size might deter potential producers. Walsh tried incorporating traditional Irish music into her script, then attempted to write a few songs with the help of a songwriter. But the show didn’t start coming together until Brielle became involved.

The composer turned the work into a “play with music.” “Himself” (minus “and Nora”) opened in Boca Raton, Fla., in 1998, with a cast of four that included Len Cariou as Joyce.

Walsh and Brielle kept tinkering, finally aiming toward creating a full-scale musical. But the project didn’t move decisively forward until about four years ago, when director Hardy became involved and challenged Walsh to focus on why she was writing it.

She remembered that Barnacle was said to have uttered over Joyce’s dead body, “You’re so beautiful.” She decided that she wanted to dramatize their lives in a way that would demonstrate what led Barnacle to say those words.

The next turning point in the project occurred when the Old Globe became interested, and the theater’s artistic director, Jack O’Brien, suggested enlisting Jeff Calhoun as the choreographer -- Calhoun’s primary occupation before he became better known for directing Deaf West Theatre’s “Big River” and “Brooklyn.”

After meeting Calhoun, Hardy -- a Tony winner (“Child’s Play”) and an Old Globe veteran -- suggested that the two of them co-direct. According to Hardy, the musical and spoken scenes in “Himself and Nora” are so closely integrated that the show required the two to work side by side.

Because co-directing isn’t common, everyone wondered whether it would be confusing.

But “it has been seamless,” Calhoun says. “We’re like an old married couple. You just put your ego away or you don’t agree” to co-direct. He laughs when he recalls their only moment of disagreement -- when an actor asked for a blocking instruction and the directors simultaneously pointed toward opposite sides of the stage. Who prevailed? “I always defer to Joe,” Calhoun says. “He has earned it.”

The directors may work together like marrieds, but it’s Brielle who has made himself most at home in the rehearsal hall -- and who relates the romance of “Himself and Nora” most closely to his own life.

He has carved out a retreat in one of the bare, cavernous rehearsal studios. His keyboard and recording equipment sit atop a swatch of carpet, accompanied by personal photos and flowers, separated from the rest of the hall by high, flat partitions.

“I couldn’t be in this huge open space without making it slightly womblike, in order to give birth,” he says, noting that four new songs have entered the world there in the last four weeks.

Born Jonathan Holtzman 51 years ago, the composer later adopted the name of his hometown in New Jersey as his professional name. He had some early theatrical success writing music for the Hume Cronyn and Susan Cooper play “Foxfire.”

Although Brielle also wrote music for plays at Circle Repertory Theatre in New York, he supported himself largely by creating music for corporate industrial shows and other commercial enterprises. He has written music for elephants, ice skaters, Rugrats, Home Depot, Las Vegas revues and now James Joyce. “It has been a heck of a ride,” he says.

This latest chapter has also brought a sea change in his life. He was transformed by a trip last August to Ireland, where he visited Joycean landmarks, rode horses through the countryside and strolled under the full moon. “Everything became very clear. It enabled me to be in a place emotionally that I needed in order to finish this.”

Swept up in the romance of it all, he was in Paris within a few weeks, proposing to his girlfriend, TV producer Cherie King.

Brielle, who has three children from two earlier marriages, admits that he knew nothing about Joyce when he started working on the project, and he says audience members “don’t have to walk in with a body of knowledge. It’s something everyone can get.” Stream of consciousness? “We allude to it, and how he would write, without getting lost in it. You will always know where you are.”

Even Walsh, the devoted fan of Joyce in her younger years, never finished reading “Finnegans Wake.” And, after years of working on “Himself and Nora,” she has begun to approach the limits of her own enthusiasm for exploring the world of Joyce.

“Now, I’m bloody tired of the guy,” she says, laughing.

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‘Himself and Nora’

Where: Old Globe Theatre, Balboa Park, San Diego

When: Opens Thursday. 7 p.m. Tuesdays and Wednesdays, 8 p.m. Thursdays and Fridays, 2 and 8 p.m. Saturdays, 2 and 7 p.m. Sundays

Ends: April 24

Price: $19 to $55

Contact: (619) 234-5623, www.theoldglobe.org