"Mama, I Want to Sing" is a family affair built upon a family dilemma: What happens when a gifted singer, raised in her father's church, wants to display her talent to the secular world?

That's the situation Doris Troy found herself in in the early '50s and it's her story that is (loosely) told in this lively show, which opened a two-week run at the Warner on Tuesday. As a family project gone public, "Mama" is not particularly slick, but despite the flaws, its down-home charm is refreshing.

The musical, now in its fourth year in New York (the Warner version kicks off the national tour), was written by Troy's younger sister, Vy Higginsen, and her husband, Ken Wydro. Higginsen, playing an omnipresent deejay, serves as the narrator; Troy plays her own mother; and a powerful young singer, 18-year-old Deitra Hicks, appears as "Doris Winter." By show's end, Hicks has been transformed from a mousy minister's daughter to a Whitney Houston-like diva. And when you remember that Houston's mother is gospel singer Cissy Houston, it makes this exploration of family/church musical tensions -- a theatrical refrain at least as old as "The Jazz Singer" -- seem all the more current.

"Mama, I Want to Sing" tends to overstate Troy's career (though her only real-life hit came in 1963 with "Just One Look," there's a suggestion that she had gold and platinum albums and Grammys). But her journey remains at once dramatic and familiar.

Black church music has been a breeding and proving ground for countless singers. Many have chosen to remain in the tradition, but popular music has also been blessed by those who have crossed over, from Sam Cooke, Ray Charles and Aretha Franklin to Jennifer Holiday and Phillip Bailey. And you only have to hear genuine gospel to realize that secular and sacred music share much in terms of technique and performance, and that pop owes a huge debt to the black church.

The plot of this "story in concert," as Higginsen describes it, is simple, its evolution as minimal as the sets. It starts in the church choir: young Doris Winter has grown up in a Pentacostal church whose music minister (Charles Stewart) is a manic, exacting figure, focusing his singers on the message of Christ even as he drives them to excellence. Stewart does a fine job of playing up the quirky methodology of such music ministers, and judging from shouts of recognition in the Warner audience, his performance hits close to home.

At this stage, Doris Winter is very much a child, unsure of her voice but anxious to please her father. Alexander Plummer Jr.'s Rev. Winter is a powerful presence, but the cadence and timbre of his sermonizing are more impressive than his singing. It doesn't help that his major vehicle is the trite "You Are My Child."

The first powerful solo comes from Kathleen Murphy-Palmer as Sister Carrie, the "star soloist" found in every church choir. On "Faith Can Move a Mountain," her voice cuts through the air like a laser, and there's no resisting either the performance or the message.

Later, Sister Carrie encourages Doris to sing "I Don't Worry About Tomorrow." At the start, she is stiff, a whisper, but halfway through she discovers her voice and begins to exult in it, taking it further and further until the teacher is left behind. Hicks sings with great power, taking a simple connective phrase like "But I . . . " and wringing every emotional nuance and musical possibility out of it. It's not just a voice her character has found, but a greater purpose, and Hicks makes the revelation believable.

From there, the conflicts are streamlined. The Rev. Winter dies, leaving Doris with a sense of responsibility to the church. But the youngster is increasingly drawn to secular music, in the form of Billie Holiday, Dinah Washington, Lena Horne and Sarah Vaughan. Doris and some of the choir members form an R&B group, the Halos. The first of three encounters between Doris and Mama Winter ends Act 1, as the title tune dramatizes their dialogue on musical values and aspirations.

The show's most adventurous moment renews that dialogue as confrontation. When Doris wins an amateur contest at the Apollo and wants to go on the road, Mama Winter reacts with a religious guilt trip, breaking into a bitter version of "Precious Lord (Take My Hand)." Doris counters with another gospel classic, "His Eye Is on the Sparrow," reminding her mother that she sings not for money but "because I'm so happy and because my spirit is free." At the end, mother and daughter are singing in counterpoint, connected even in their distance.

Unfortunately, "Mama, I Want to Sing" doesn't sustain that moment: Having given us mostly memorable gospel, it sinks to mediocre pop. Even "Just One Look" fails to impress, sounding a bit dragged out compared with the original. Hicks is a bit stiff in moving from sacred to secular ground, but when she cuts loose and lets her powerful instrument fall into the service of a more powerful message, she can produce unearthly swoops and piercing high notes that reveal where her talent and inspiration lie.

Troy makes the most of her moments on stage, sounding quite earthy and bluesy compared to the other cast members. There is something engagingly genuine and unaffected about her performance, which under the circumstances is less performance than self-realization. Throughout the show, the fine 15-member choir serves a number of dramatic functions, enveloping the whole affair with the genuine warmth at the center of gospel's theology of hope and salvation.

Like the films "Say Amen Somebody" and "Gospel," "Mama, I Want to Sing" extends the public's exposure to a powerful American institution, the black church, and to the excitement of gospel music. Judging from the reaction of the opening-night crowd, the show is more confirmation than revelation -- but it makes for a joyful evening.