THE GOSPEL musical revue "Mama I Want to Sing" is by turns exhilarating and exasperating. At the Warner Theater, New York's longest-running black musical is a true family affair, written, produced and directed by Vy Higgensen, who celebrates the story of her sister, R&B singer Doris Troy.

Troy developed her spectacular pipes in Harlem's Mount Cavalry Church gospel choir and, against her mother's wishes, went on to develop a pop music career that included the hit "Just One Look."

In its best moments -- and there are many -- "Mama," more a staged concert than a play, has poignant scenes and honest, unaffected performances. And the show rocks with joyful, rafter-shaking tumult. But at more than 2 1/2 hours, the show is overlong, and the performers too often slide into vocal excess, to the point where it migbt well be retitled, "Mama I Want to Scream."

Playing the young Doris Troy, Deitra Hicks can instantly and impressively ascend from a girlish whisper to a piercing siren wail, adding curlicue embellishmentsto a voice that sounds like Deniece Williams'. But she gets carried away with some of her earsplitting histrionics. Playing her own mother, Doris Troy is a vocal powerhouse and a natural actress, pouring her abundant anxiety, anger and love into "Precious Lord," which had mothers in the house cheering loudly and assenting with "amens." The large cast whips up gales of energy, and "Mama" comes most fully to life in its vigorous and supremely controlled choir scenes.

There can be too much of a good thing, however, and "Mama" wears out its welcome early in the second act. Little new ground is broken with some of the overstretched songs, and the sketchy narration/song/narration structure takes its sweet time wandering through Troy's early life, but devotes a mere two songs to her commercial career.

But for all its flaws, this homespun, humble "Mama" is a houserocker and a heartwarmer. It is likely to return to the Warner later this spring.

MAMA I WANT TO SING -- At the Warner Theater through Sunday.