Lee Mikeska Gardner in ’Souvenir: A Fantasia on the life of Florence Foster Jenkins’ at 1st Stage. The show runs through March 2, 2014 in Tysons Corner. (Teresa Castracane)

Florence Foster Jenkins — the socialite-turned-soprano — has a solemn warm-up routine. Looking religiously intent, she flexes and massages her jaw. She touches her fingers delicately to her ribs, as if readying her breath support. She draws an invisible plumb line upwards from the top of her scalp, perhaps imagining that her posture aligns with a star. Then she, for lack of a better word, sings.

As channeled by a spot-on Lee Mikeska Gardner in 1st Stage’s enjoyable if occasionally dawdling production of “Souvenir: A Fantasia on the Life of Florence Foster Jenkins,” Madame Flo’s arias are wildly and exuberantly off-key. Pitches, rhythms — heck, entire melodies — careen spectacularly away from the composer’s intent in a gush of romantic feeling. But what makes her recitals irresistible is Jenkins’s unshakable conviction of her own artistry. She believes she commands one of the 20th century’s great coloratura voices. It’s a belief that is, on some level, inspiring.

“I found myself hoping some of her certainty would rub off on me,” her bemused accompanist Cosmé McMoon (Brian Keith MacDonald) remarks as he recalls his 12-year collaboration with the singer.

Jenkins was a real life figure (1868 to 1944) who packed recital halls with audiences eager to hear her notoriously tone-deaf technique. For those in the seats, the sessions were hilarious, but Jenkins apparently never realized that her listeners were reacting with anything but admiration. At least, she didn’t realize that awful truth before her 1944 concert at Carnegie Hall, a few weeks before she died. Whether she cottoned to it even then is a question that adds suspense and poignancy to Stephen Temperley’s play, which is directed here by Jay D. Brock.

Given its subject matter, of course, much of “Souvenir” is comic, and Gardner teases out the humor without removing Jenkins from the sphere of empathy. In addition to generating musical mayhem (Jane Margulies Kalbfeld and Rachelle L. Fleming served as the production’s vocal coaches), Gardner speaks with the right affected articulations, and she glides on and off stage with a decorous self-importance suggestive of overly moneyed ease.

Her funniest moments, not surprisingly, come in the Carnegie Hall sequence, when she turns up in elaborate costumes — including a French maid’s uniform, military garb and an angel’s outfit, complete with wobbly pipe-cleaner halo — and makes ridiculous mannered gestures with a dagger and other props. (In addition to contributing to these moments, the production’s costume designer, Yvette M. Ryan, guides Jenkins’s daywear choices through the styles of the 1930s and ’40s over the course of the play.)

Usually seated at the onstage piano, exuding an air of quiet, cultured amiability, MacDonald gracefully reveals McMoon’s painfully mixed feelings about his longtime associate: The accompanist cringes at Jenkins’s vocal ineptitude and her sheer gall, and yet he feels increasingly fond and protective of her.

Temperley has created perhaps a little too much space for such pensive ambivalence in “Souvenir”: Brock and MacDonald might consider tightening the pace of McMoon’s initial wistful, keyboard-tickling monologue, which gets the production off to a slow start. As Madame Flo remarks in the play at one point, it’s a matter of perfecting and refining.

Wren is a freelance writer.

Souvenir: A Fantasia on the Life of Florence Foster Jenkins

By Stephen Temperley. Directed by Jay D. Brock; sound, Gregg Martin; lighting, Baron Pugh; set, Mark Krikstan; technical director, Aaron Fensterheim. About two hours and 10 minutes. Tickets, $15-$27. Through March 2 at 1st Stage in Tysons, 1524 Spring Hill Road, Tysons Corner, Va. Call 703-854-1856 or visit www.1ststagetysons.org.