In a Broadway season notable only for what appears to be terminal anemia, "Ma Rainey's Black Bottom" (at the Cort Theatre) is not just a shot in the arm. It amounts to a veritable transfusion.

Throbbing with vitality and the kind of dialogue that burrows into the marrow, August Wilson's drama charts the storms that erupt one day in 1927 in a Chicago recording studio, where Ma Rainey, the legendary blues singer, is cutting such songs as "The Black Bottom" and "Moonshine Blues." Going behind the scenes to reveal the nuts and the bolts of show business as they come together -- or come loose -- has always been a particularly theatrical tactic. But if Wilson is opening doors generally closed to the public, it's not just to catch performers with their public masks down.

This is the "race division" of a white-owned and white-run recording company. And while the business at hand is getting Ma Rainey's voice on wax -- and her signature on the mandatory release forms -- the real dramatic business is the growing sense of checkmate that weighs on Ma and the four members of her backup band. All of them know instinctively that their usefulness, and whatever momentary civilities are being extended, will come to an end as soon as the afternoon session does.

Like Charles Fuller's "A Soldier's Play," Wilson's play builds to a particularly violent revelation of the boomerang effects of racism. The whites in "Ma Rainey's Black Bottom" are all out of reach. The blacks must deal among themselves with the frustrations and injustices regularly meted out by a society that uses them only to make a buck. At the end, a knife flashes in the dank basement that passes for the musician's warm-up room. Black lashes out at black, stupidly, unknowingly, because there's no other target in sight. No other target is permissible.

Other plays have come to such bloody, melodramatic ends. What is remarkable in Wilson's work, his first for the stage, is the richness of its texture and the variety of its tone along the way. If the humor is savage in places, it is frankly robust in others. Red-hot anger exists alongside cool irony. The edginess overtaking the musicians as they wait in the basement for one of Ma Rainey's purposeful tantrums to pass does not preclude a farcical episode once they all get back up in the studio itself, and Ma insists that her nephew, a hopeless stutterer, speak the introduction to one of her numbers.

To Wilson's characters, music is music, but so is talk, and their banter ranges freely from the trivial to the blasphemous. So authentic does it sound coming from the mouths of a superlative cast that Wilson is already being hailed as a major new "voice" in the American theater.

The evidence is persuasive. The only thing that holds "Ma Rainey's" power partially in check is the work's rambling stop-and-go structure. Wilson seems at times to have written two plays and not been able to marry them as firmly as he wished. The two parts are, in fact, clearly delineated by Charles Henry McClennahan's splendid set: a vintage recording studio, to one side; to the other, the musician's basement retreat, with its seeping pipes and rusty lockers.

Ma Rainey (Theresa Merritt) presides -- indeed, reigns -- over the former locale. Her ample body ashimmer with pink beads, a band of diamonds blazing from her forehead, she is a down-home mama masquerading as royalty. Mention Bessie Smith to her, as one of the musicians does, and she arches a regal brow and barks, "Bessie what?" She demands that the white men address her as "Madame Rainey," run her errands and -- don't they know she can't sing without a soft drink in her hand? -- fetch her a Coke.

But Ma is no fool and her imperiousness is only the momentary strategy of a black woman who, as long as she can delay the recording session, holds the balance of power. Once the record is pressed and studio executives have what they want, she understands she's no better than a whore: "They roll over and put on their pants," she observes dispassionately, preferring to save up her anger for more pragmatic purposes. Merritt's autocratic flamboyance makes her performance wildly theatrical; but it is the unflinching self-knowledge that gives it its depths.

Meanwhile, on the other side of the stage, Ma's backup musicians -- a trombonist (Joe Seneca), pianist (Robert Judd), bassist (Leonard Jackson) and trumpeter Once the record is pressed and studio executives have what they want, Ma understands she's no better than a whore: "They roll over and put on their pants," she observes dispassionately. Charles S. Dutton) -- are waiting for Ma to get her act together and passing their time in not-so-idle chatter. They all have their own stories to spin and gripes to grind. But it is the trumpeter -- Levee by name -- who threatens the afternoon's equilibrium. His expansive bravado borders on aggression and his jocularity bristles with anger.

Levee is not content to reap $25 cash for playing Ma's "jug band" arrangements. He wants to have his own band, compose his own music, stand proud and independent in the pair of $11 shoes he's just purchased. The white studio owner has expressed an interest in Levee's career, or so Levee thinks, and his recklessness swells with his ambitions. He questions Ma's old-fashioned arrangements and dares to put the make on her dim lesbian lover. The passiveness of his fellow musicians spurs his ridicule. He even assaults the deity, accusing Him of throwing a black man's prayers "into the garbage."

It's a powder keg of a role, just waiting to explode, and Dutton detonates it adroitly. Without once hiding Levee's rage, Dutton succeeds for much of the play in passing the character off as a gloriously extroverted bonehead. Then Wilson begins snuffing out Levee's dreams one by one, and the life of the party becomes the death of the party, a whirling dervish, entangled in frustrations so suffocating he can only cut free of them them with a knife. Dutton's performance -- volcanic fury coated with deceptively raucous spirits -- will surely be remembered at Tony time.

You may, however, have sensed the problem. Wilson's play is ruled by two equally commanding creatures, each battling it out on separate turf. Although Ma Rainey and her musicians come together periodically for the actual recording sessions (the actors are also accomplished musicians and their music is swell), the traffic between their two worlds is minimal. The power generated in the studio does not necessarily carry over into the band room, and vice versa. Repeatedly, the play halts here, so it can begin anew over there. Divided in its loyalties, it ends up dividing its impact.

Director Lloyd Richards, however, has given the work a masterful staging, as alert to the day's passing behavior as it is to the years of accumulated humiliation that have gone before. To the extent that "Ma Rainey" does seem all of a piece, it is because the actors, interacting with a kind of casual familiarity, constitute a natural ensemble. Indeed, there's an easygoing alliance among them that belies the brewing tempest. Wilson's characters know this session won't make them; they just want to get it over with and collect their dough. Only Levee has dreams, and they will prove lethal.

Even in the best of years, "Ma Rainey" would command attention. But at a time when Broadway can muster no more than a couple of openings a month -- and then a silly, spendthrift musical like "The Three Musketeers" or a reactionary sex comedy like "Alone Together" -- it stands out, and very nearly alone, for its integrity and its insight. It may be premature to hail Wilson as the next savior of the American theater, as more than a few New York critics have already done. But it is undeniable that he has redeemed what, up to now, has been a shockingly bankrupt season.