“WILD ROSE”

****

(R, 1:40)

Rose-Lynn Harlan, the fiery-haired heroine of the hugely satisfying kitchen-sink fairy tale “Wild Rose,” isn’t the kind of gal who whistles while she works. She sings while she vacuums, crooning her favorite country tunes, her voice a startling distillation of raw talent and emotion. For a brief moment reality fades from view, and the foyer she’s cleaning becomes a stage.

Rose-Lynn shares her star-is-born aura with Jessie Buckley, the extraordinary Irish actress playing her. The foyer belongs to her wealthy employer, Susannah (Sophie Okonedo), who takes a fanciful interest in her musical abilities and decides to play fairy godmother. But Rose-Lynn’s chances of realizing her dreams seem as far away as Nashville, the country-music mecca she’s long pined for from her hometown, Glasgow.

“I should have been born in America,” she frets, bemoaning the fact that the only other person on this side of the Atlantic who gives a damn about country is the legendary radio host Bob Harris (who later makes a lovely cameo). She doesn’t yet realize that the absurdity of her situation — being a Scotswoman with a passion for country music — is precisely what makes her gift so indelible and unique.

She’ll figure it out soon enough. Harlan Howard’s fabled formula for the country genre — “three chords and the truth” — means so much to Rose-Lynn that she’s had it tattooed on her arm. That mantra could also describe “Wild Rose,” which, like most good country tunes, is a simple, skillful arrangement of tried-and-true notes that are no less affecting for being so familiar. The screenwriter, Nicole Taylor, and the director, Tom Harper, compose their story in clean, stirring melodic lines that they return to again and again, treating Rose-Lynn’s many setbacks — as well as her small, crucial steps toward growth and self-discovery — like subtle variations on a refrain.

That fall-backward-stumble-forward rhythm is a natural one for Rose-Lynn. When we first meet her, she’s striding out of the prison where she spent 12 months for attempted heroin smuggling, a smile on her face and an ankle monitor beneath her boots. She’s only 23 and eager to slip back into some of her life’s comforting routines, including hooking up with on-and-off boyfriend (James Harkness) and singing with her band at Glasgow’s Grand Ole Opry.

But not everyone is willing to welcome Rose-Lynn back, at least not on the same terms as before. She has two young kids — their names, in a nice touch, are Wynonna (Daisy Littlefield) and Lyle (Adam Mitchell) — who have spent the past year living with their grandmother, Marion (Julie Walters), and they’re not thrilled to be back in their mother’s care. Marion regards her daughter with a wary distrust.

Buckley came to fame singing show tunes and pop ballads on the BBC talent show “I’d Do Anything.” But she brings more than just a powerful set of pipes to this role; she finds the emotional coherence in an array of seemingly contradictory moods and impulses, showing us how Rose-Lynn’s brash, swaggering confidence goes hand-in-hand with her crippling insecurities. Those contradictions come to the fore when she finds herself on the receiving end of Susannah’s attention.

Living a life of ease and boredom with her husband and their two kids, Susannah becomes determined to nurture and eventually finance Rose-Lynn’s talent. She knows nothing about country music, just as she knows nothing about Rose-Lynn’s family life or her time behind bars, setting up expectations that are bound to be disappointed.

Their scenes together are the heart of the movie, in part because Okonedo touches so many deft and delicate notes: She nails the warm, fluttering tones of a woman who leads a life of undeniable privilege, but she also makes it impossible not to admire the warmth and utter sincerity beneath Susannah’s do-gooder act.

The story builds to a wrenching series of shifts and reversals — physical, emotional, tonal, musical. (The country-stuffed soundtrack includes several original songs, including a showstopper written by Mary Steenburgen, Caitlyn Smith and Kate York.) But the crowd-pleasing spirit that animates “Wild Rose” is also, happily, a spirit of nuance, and Rose-Lynn’s soul searching leads her to an honest, hard-earned understanding of who she is and who she is destined to become.