"La Cage aux Folles" belongs to the old-fashioned school of Broadway musical comedy that prizes songs, dances, jokes, opulent costumes and a line of statuesque chorus girls, most of whom, oops!, happen to be boys.

It's all about love and caring and learning to respect your parents, even if they are, omigosh!, both of the same sex.

The "oops" and the "omigoshes" may lend "La Cage" a certain piquancy for the 1980s, but make no mistake about it. If you discount the confusions of gender, its sentiments would not be out of place on a Victorian sampler. At a time when the Stephen Sondheims and the Andrew Lloyd Webbers are edging the musical into the future, the Tony-winning creators of "La Cage" -- composer-lyricist Jerry Herman and playwright Harvey Fierstein -- are nudging it back to the good old days, when a show was deemed worthy if it picked up your spirits, gladdened your eye and gave you something to hum on the way up the aisles.

By that sequined tape measure, "La Cage," which began an open-ended engagement at the National Theatre last night, is, indeed, giddy, gaudy and rather grand. And it features a stupendous performance by actor Keene Curtis, who, as the toast of a transvestite nightclub in St. Tropez, looks like the crumbling statue of a lesser-known Roman goddess named Temperamenta and carries on like a combination of Truman Capote, Gloria Swanson and Hermione Gingold. Although Curtis' costar, Peter Marshall, gives a performance of lesser dimensions, those who know him mainly as a TV game-show host will be pleasantly surprised by the vigor of his singing voice.

Where "La Cage" goes wildly askew is in the telling of its story. Inspired by the hit Parisian play of the same name (which in turn spawned two hit movies), Fierstein's book is broad even by the most tolerant definition of farce. Georges (Marshall) and Albin (Curtis) are two happy, aging homosexuals who together have raised Jean-Michel, Georges' son and the product of a long-ago, one-time-only backstage fling at the Lido. Now Jean-Michel has fallen in love and wants to bring his prospective in-laws home for a get-acquainted dinner.

The would-be in-laws turn out to be a rabid right-wing politician, who heads the TFM party (for Tradition, Family, Morality) and his priggish, sexually repressed wife. Since their prospects of taking to Albin, Jean-Michel's surrogate "mother," are about as good as Jerry Falwell hitting it off with Divine, Albin must disappear for the evening or at least tone down his wardrobe and put some starch in his wrist.

None of this is particularly subtle, but by the second act, when the politician and his spouse come to call, the buffoonery comes dangerously close to imbecility. About all director Arthur Laurents can do at this point is keep chaos at bay. Nor does it help that the waspish retorts that gave Fierstein's "Torch Song Trilogy" its bite are fairly innocuous here. Informed that Jean-Michel is going to get married, Albin can only wring his hands and moan in a tone worthy of Medea, "Where, where, oh where did we go wrong!"

What saves "La Cage" time and again is the singing and dancing. Herman has always had a gift for writing tunes that lodge in the mind after the first hearing and his score is as profligate with melody as a hurdy-gurdy drunk on champagne. "Song on the Sand" may well be the first ballad in a Broadway musical sung by one man to another, but more striking in these days of vanishing ballads is its simple, unaffected beauty. "The Best of Times," like the title number from "Dear World" or "Hello, Dolly!," takes a joyous refrain, then brings it back a half-dozen times -- adding voices, changing the key and turning up the volume in the process.

The two strongest songs in the score (which is to say the most dramatic) go to Albin, better known as Zaza to the nightclub patrons. No less than Mame or Dolly, Zaza merits a niche in Herman's pantheon of unconventional, outsized women who live by their own rules. "A Little More Mascara" charts his dressing-table transformation from man to woman, and "I Am What I Am" allows him to defend himself with fervent pride. Curtis mines the first for its outrageous humor, as he slips into high drag; in the second, he manages a considerably more difficult chore: He invests Zaza, who can easily be viewed as a ridiculous creature, with blazing passion and searing dignity. The number closes Act 1 on a fever pitch that "La Cage" never quite recaptures after the intermission.

The show's other trump card consists of the most astonishing chorus line since "A Chorus Line" -- 10 females billed as "Les Cagelles." Actually, eight of the 10 are female impersonators, not that you can tell by their legs. Choreographer Scott Salmon puts them through a sensational cancan. Always an outrageous dance, it is in this instance even more outrageous, when you realize that under the Toulouse-Lautrec wigs and the scalloped skirts, those are men thumping their breasts and emitting the traditional yelps as they come crashing to the floor in the requisite splits.

Theoni V. Aldredge's ostentatious costumes and David Mitchell's flashy sets -- from the port of St. Tropez under the blinking stars to the nightclub stage under hot pink spotlights -- make "La Cage" an eye popper. The production numbers flood that stage with beads, bodies, boas and a double-jointed angularity that suggests the Folies-Berge re in a raffish mood. This is the sort of garishness that gives bad taste a good name.

Curtis dominates the show not merely with the force of his outlandishness, but, surprisingly, with the delicacy of his emotions. In that sense, the performance is a paradox -- the grand histrionics serving to define a character who is really shy, insecure and needy. Marshall is not so gifted an actor; his sincerity is real enough, but it does not come effortlessly. You can see him working at it.

The supporting cast is a mixed bunch, too, although I suspect some of the difficulties spring from the script, which treats certain characters more cartoonishly than others. Ronald Dennis, as the butler who wants to be a maid, dwells on the outer limit of caricature; so do Bob Carroll and Pamela Hamill, as the politician and his wife. Juliette Kurth, on the other hand, makes a fairly bland fiance', and Le Clanche' du Rand is colorless as an obliging restaurant owner. Far more appealing than his Broadway counterpart, however, is Peter Reardon as the ungrateful son who momentarily turns his back on Albin -- just, you may recall, as Patrick Dennis once did on Mame.

He will, of course, come to see the error of his ways. For "La Cage," while pretending to introduce us to an exotic subculture, is really as conventional in its values as "I Remember Mama." The only feathers that risk being ruffled at the National are those worn by the extraordinary ladies/gentlemen of the chorus.