Sleek as it is, tough-minded as it pretends to be, "Dreamgirls," the 1981 Tony-winning musical that opened Thursday night at the National Theatre, has a heart right out of "42nd Street."

One of the ironic refrains in this saga about the rise of a spangled singing group not unlike the Supremes maintains that "show business, it's just show business." But it's abundantly clear that for the creators of "Dreamgirls" -- director-choreographer Michael Bennett, book and lyric writer Tom Eyen and composer Henry Krieger -- no other business can hold a candle to it.

Although the musical wants to chronicle the cool betrayals, the ruthless manipulation and the shady deals that underlie the glitter of superstardom, the toughness is only skin deep. "Dreamgirls" subscribes to the time-honored belief that you can go out on the stage a bumpkin and come back a star. Did you ever think you'd hear the line "We open in Cleveland in a month?" delivered with perfectly straightforward urgency in the 1980s? Or this equally earnest couplet, "You've got that air/ They know a star is there."

Well, you'll hear them -- and more -- in "Dreamgirls," where the jitters and heartache of becoming America's top singing group are fundamentally no different from those experienced by Mickey and Judy putting on a show. What is different is the directorial expertise with which Bennett, aided by a megatalented cast, has converted this material into a seductive spectacle about fame. "Dreamgirls" takes old saws and polishes them to a mirrored gleam.

More and more, the Broadway musical seems to be adopting the fluidity of the cinema -- a development for which "Dreamgirls," as much as any recent show, is responsible. No longer the old stop-and-go rhythms. Here, dialogue blends into song, which then eases back into dialogue, as if oblivious to the interruptions of applause. Robin Wagner's extraordinary scenery -- four towers encasing a battery of lights -- glides furtively about the stage. The towers don't move of their own accord, as they did on Broadway; the actors push them into place. But the effect of space constantly being redefined before our very eyes -- sometimes in midsong -- remains mesmerizing.

Bennett uses all the tools of the movies -- wipes, dissolves, close-ups -- not only to portray the fabulous ascension of the Dreams, but also to chart the emergence of rhythm and blues as mainstream music. The personal traumas in "Dreamgirls" may border on old-fashioned soap opera. But it is soap opera given a sexy, high-tech, high-gloss look.

The story intertwines the professional and private lives of the Dreams, their boyfriends, their calculating manager, their composer, plus assorted moguls and performers, some on the fast track up, others on the slow skid down. Deena (Deborah Burrell) has ambitions that go beyond being lead Dreamgirl. ("I want to be more than an entertainer," she tells her manager. "I want to be an artist.") Spunky Lorrell (Arnetia Walker) is locked into a no-win affair with a married soul singer (Herbert L. Rawlings Jr.), who could probably double for James Brown.

But the biggest tempest swirls around Effie (Sharon Brown), the rotund rhythm and blues singer, who is demoted from lead to backup singer, and then, when the big contracts start rolling in, is bumped from the group altogether for a svelter Dreamgirl. Effie will have the solace of a career on her own, but not before she hits rock bottom and pours all her frustration and anger into "And I Am Telling You I'm Not Going," the potent first-act finale.

This is the number -- a rock aria, almost -- that made an overnight star of Jennifer Holliday, who virtually blistered the walls with her raw power. Brown doesn't have that kind of force, but she is a persuasive actress. Collapsing at her dressing table in Las Vegas, she snarls her anger at having been dumped, pleads ignominiously to be kept on and then builds to a shattering climax as she confesses her love for the very manager who has engineered her dismissal.

Played by Weyman Thompson, that manager is the smooth mastermind behind the Dreams, and expediency surely figures in his decision first to seduce Effie and then to marry Deena. As jealousies and recriminations build, Thompson remains composed and natty -- the evil eye of the storm. Playing his cards close to his chest, the actor proves as vivid as those who are letting out all the stops. Rawlings lets out more than anyone -- strutting, squealing, kicking and moaning as the soul singer who refuses to bottle up his energy for the well-heeled crowd and goes mildly berserk at the National Democratic Fundraiser.

Despite such outpourings of energy, this production is sparer and leaner than the Broadway version, which turned out to be too costly to tour. The big numbers have lost some of their multilevel opulence. (Perhaps to compensate, Bennett has added several dance segments to the proceedings.) Theoni V. Aldredge's costumes, however, continue to contribute immeasurably to our perception of the Dreams as fabled creatures of artifice and exotica.

Starting out backstage at the Apollo Theater in frumpy gold lame' dresses and ill-fitting wigs, they eventually emerge as profane goddesses -- draped in beads and fur that show off their come-hither thighs. Unlike many musicals about show biz sensations, "Dreamgirls" actually does convince you that this trio could have commanded the ovations, the adulation and the packed press conferences that dot Eyen's script. While Krieger's score is for the most part undistinguished, he has given the Dreams a medley of insinuating songs that throw their synchronized sex appeal into sharp relief. Burrell, in particular, is a true beauty, and her transformation from sweet innocent to Vogue cover girl is one of the more stunning aspects of the evening.

Those who came of age during the 1960s will no doubt find "Dreamgirls" a source of rich, rewarding pleasures. Indeed, for a show that bills itself as the musical of the 1980s, it emits the decided scent of nostalgia and an overriding affection for the days of platform shoes and payola. Presumably, it is telling us that the entertainment industry is populated by sharks with pearly cuff links, that greed and ambition prevail and that performers are molded into bestselling artists only to be tossed aside once their earning power declines.

But its cynicism is a pose. It really believes you can pick yourself up, dust yourself off and climb right back up the charts again. The heavies get their comeuppance. The others get comebacks.

Dreamgirls. Book and lyrics by Tom Eyen. Music, Henry Krieger. Directed and choreographed by Michael Bennett. Sets, Robin Wagner; costumes, Theoni V. Aldredge; lighting, Tharon Musser. With Sharon Brown, Deborah Burrell, Lawrence Clayton, LueCinda RamSeur, Herbert L. Rawlings Jr., Larry Stewart, Weyman Thompson, Arnetia Walker. At the National Theatre through June 7.