A few quibbles aside, the musical Waitress plays and sounds like it’s close to ready for the Broadway big time.

Waitress. Music and lyrics by Sara Bareilles. Book by Jessie Nelson. Based on the motion picture written by Adrienne Shelly. Directed by Diane Paulus. Choreographer, Chase Brock. Music supervisor, Nadia DiGiallonardo. American Repertory Theater, Loeb Drama Center, 64 Brattle Street, Cambridge. Through September 27.

Jessie Mueller in the American Repertory Theater production of “Waitress.” Photo: Evgenia Eliseeva

By Evelyn Rosenthal

The road from movie to musical (and, often, back again) is well trod these days. To the successful musical adaptations of movies like The Producers, Hairspray, Once, Kinky Boots, and Finding Neverland, we can add one more: American Repertory Theater artistic director Diane Paulus’s revisioning of writer/director/actress Adrienne Shelly’s 2007 independent film Waitress. The charming, funny, and, yes, sweet film about a pregnant, pie-making waitress in a diner somewhere in the South makes its smashing transition to the stage in the A.R.T.’s production. A Broadway run has already been announced (previews in March, opening in April), and if the producers know what’s good for them and the public, they’ll bring along much of the current cast, led by the phenomenal Jessie Mueller.

The Tony-winning Mueller (Carole King in Beautiful) brings warmth and grit — not to mention a stunning voice — to the role of Jenna Hunterson (played in a cooler, dreamier key by Keri Russell in the film). Jenna’s pie-making serves as both an escape from the disappointments of her life with a controlling, abusive husband, and as an expression of love (her mother taught her how to bake), selfhood, and art. That may sound like a lot of emotional weight to hang on the making of pies, but it’s leavened with sharp comedy. For that we have to thank the book by film director Jessie Nelson (I Am Sam), which includes heaping helpings of Shelly’s original screenplay (having recently rewatched the film, I recognized large swaths of her wonderful wry comic dialogue), as well as the well-wrought lyrics by singer-songwriter Sara Bareilles, who composed the score.

The musical’s story is virtually the same as the film’s: the unhappy Jenna finds herself pregnant by her loutish husband, Earl (Joe Tippett), dreams of winning a pie contest to fund her escape, has an affair with her ob/gyn, the married Dr. Pomatter (Drew Gehling), gets some unexpected help from diner owner Joe (a crusty but, thankfully, not overly folksy Dakin Matthews), and starts a new life—make that two new lives. Most of what the show’s creators have changed or added works very well. If Paulus’s production leans heavily on the comedy—including deft touches of slapstick, especially by the appealing Gehling—she does it without diluting the seriousness of the predicament faced by Jenna and countless other women.

A few characters have been given intriguing makeovers. Jenna’s friend and fellow waitress, Becky, is played in the film by the slim, blonde Cheryl Hines as a bit of a vamp, with an invalid husband she cheerfully cheats on. The musical’s Keala Settle, a larger woman who, according to her bio, is part Maori, gives the character a sassy earthiness that matches her big, R&B-flavored voice, and roots her actions in a clear-eyed view of love and its limits. Also effective is the transformation of the third waitress, Dawn, from Adrienne Shelly’s endearing ditz to an equally endearing History-Channel-watching, Revolutionary-War-enacting nerd. Jeanna de Waal is terrific as the would-be Betsy Ross searching for her Paul Revere and finding him in Ogie (Jeremy Morse). Morse’s portrayal tones down the creepiness of the movie’s Ogie and turns up the adorableness of the suitor Dawn calls a “mad stalking elf.”

Jessie Mueller, Jeanna de Waal, and Keala Settle in “Waitress.” Photo: Evgenia Eliseeva.

Another plus is the more prominent role given to Dr. Pomatter’s nurse. Charity Angél Dawson (listed as part of the ensemble) gives a comic boost to Jenna and the doctor’s office trysts. On the other hand, some added backstory—a few lines about how Jenna ended up with Earl because he took her in when she had nowhere else to go—seemed superfluous and raised more questions than it answered (why and how did she end up in that position?). And when Cal (Eric Anderson), the cook and Becky’s love interest, sarcastically responds to someone, “I’ll Twitter about it,” we’re being told a little too self-consciously that we’re not in 2007 anymore.

A few such quibbles aside, the musical plays and sounds like it’s close to ready for the big time. Bareilles’s fine score—her first musical—draws on popular genres from Broadway-style ensemble numbers to country, R&B, and doo-wop (with a “Be My Baby” bass line), and features a gorgeous, showstopping ballad in “She Used to Be Mine.” She seems to have a knack for musical theater, which she has called her “first love.” The autobiographical insights of her well-crafted pop evidently served her well in creating songs that deepen each character, with heartfelt, clever, funny lyrics that are smoothly integrated into the movement of the play. A couple of songs in the second act are not as strong as they could be and veer toward the sentimental (“Take It from an Old Man” and “You Matter to Me”), and the ensemble number “Opening Up” suffered from bass-thumping overload (the lyrics were hard to make out). But overall, it’s a first-rate score, and some of the songs really shine.

As for looks, it’s always a challenge to fit the wide range of film spaces onto a theater stage, but scenic designer Scott Pask and lighting designer Kenneth Posner have managed to achieve a satisfying cinematic effect. Most of the action takes place in Joe’s Diner, which they have opened up beautifully, with windows looking out on a spare vista of telephone poles and wires against a sky that changes with the time of day. Transitions from the diner to Jenna’s home, a bus stop, the doctor’s office, and the hospital are swift and seamless. The set easily accommodates the five-piece band which, while not specifically integrated into the story, fits into the diner setting—it’s a roadhouse band camping out in one of the seating areas.

Though Shelly, sadly, did not live to see her film’s success, Paulus, Nelson, Bareilles, the production team, and the top-notch cast have shaped Waitress, the musical, into a touching and thoroughly enjoyable slice of down-home self-discovery that pays loving tribute to her vision.

Evelyn Rosenthal is the former editor in chief and head of publications at the Harvard Art Museums. She is also a professional singer, specializing in jazz and Brazilian music. She writes about musical theater, books, and music for the Arts Fuse.