Billy (Aaron Finley) and Barbara (Whitney Bashor) have a complex romantic relationship in Signature Theatre’s “Diner.” (Carol Rosegg)

In “Diner,” a new musical based on the 1982 movie, Tess Soltau got to build her character from the ground up. The waist up, rather.

“Elyse has no lines in the film,” Soltau says. “And you only see her legs. It’s like the Charlie Brown adult — ‘whanhn-WHANHN, whanhn-WHANDN.’ ”

“Diner,” making its world premiere at the Signature Theatre, is still set in 1959 and still primarily about six guys, all friends from childhood, who reunite for a wedding and hang out in a Baltimore diner. The men, all in their 20s, discover that getting older doesn’t mean they have a clue how to grow up.

But as one might expect from a show with music and lyrics by Sheryl Crow (the film’s writer-director, Barry Levinson, wrote the script), women have been promoted from minor to major roles.

Their peripheral stature in the film was an advantage when it came to articulating the three expanded female roles: Elyse, Barbara (Whitney Bashor) and Beth (Erika Henningsen).

“At least speaking for myself, it seems there’s less pressure on us than for the guys,” Bashor says. “Those characters are so iconic and I think we almost have a more lenient experience. We aren’t bound to what the movie was in any way.”

The basic outlines of the characters match the film’s. Elyse is engaged, but can only walk down the aisle if she passes a quiz on the Baltimore Colts written by her fiance. Career-oriented Barbara finds herself unmarried and pregnant. Beth is a housewife who longs for something beyond her own front door.

Beth’s was the most substantial female part in the original. “My role was played by Ellen Barkin,” Henningsen says. “There’s this iconic scene with her and her husband where they talk about records and, reading it for Barry, I was terrified. And he actually said, ‘This is not the movie put on stage. This is a brand-new expression of ‘Diner.’ ”

Obviously, one of the biggest differences is that people burst into song, which gives the women more chances to shine.

“There are these very strong, female-point-of-view ballads that make a very clear statement, and I think that’s absolutely because Sheryl is a strong woman herself,” Bashor says.

The music also illuminates the experiences of women of the time period in general. The song “Tear Down This House,” about how being a housewife sucks, “encompasses what I think a lot of women at the time were feeling,” Henningsen says. “So it’s not a song just for me — it becomes a song for that whole generation.”

Signature Theatre, 4200 Campbell Ave., Arlington; through Jan. 25, $75-$100.

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