OH, KAY! - Through Sept. 23 in the Kennedy Center Opera House.

"Oh, Kay!" is not the answer.

The questions was: What ever happened to the good old American musical comedy, with its high stepping chorus and singable tunes and dress-up costumes and clean romance?

"Oh, Kay!" an adaptation by Thomas Meehan of a 1926 George and Ira Gershwin musical with other Gershwin songs added, has all of those ingredients, and there is a certain pleasure in watching a lot of cheerful people bounce about in that wonderfully vulgar pop fantasy of carefree life among the "socialites." Obviously, it has, or had, some style.

But it takes a certain kind of dash to be able to carry off an old style. The way it is worn indicates whether the reviver considers it classic, transcending its time, or camp because it expresses a period on which we now have some perspective.

This production preposterously tries to do the former. The latter may not have worked - we are in no position to sneer at successfully tuneful exuberance - but giving fullscale historical treatment to a once-serviceable but now out-dated vehicle is silly. It's one thing to love and collect old automobiles, but another to expect an out-moded runabout to keep up with modern traffic. And this is still true even if the old car was well crafted and the new ones shoddily made.

The story of "Oh, Kay,'" which is one a level with its title, is about an English aristocrat named Kay, all heart and no money, who is in the bootlegging business with a big man named Shorty, who is holding off gangsters, government agents and others he is conning by pretending to be the butler. The jokes run to "If it's the wrong number, how come you answered the phone?" and "When Repeal comes, it isn't going to be any fun getting drunk," and having twins dashing around making people think they're seeing double. And the ultimate in graceful, romantic dialogue is, "You sure would make a beautiful bride."

It's also true that the hyrics - "I could jump for joy/I'm a lucky boy" - are pretty dreadful when examined, and yet such songs as "Someone to Watch Over Me," "Fidgety Feet," "I've Got a Crush on You" remained popular. They don't stop this show, though, probably because, by being treated as important, they seem particularly trivial.

So the mistake here was in making a fullscale production of the show. It is augmented by the problems of actors. Jane Summerhays, doing the title role that was originally Gertrude Lawrence's, is better at being Lady Kay pretending to be the maid than she is at pretending to be a lady. Jack Weston has some funny moments in, around and sometimes above or below those appalling comic lines, but he is trying two approaches - the naive and the Don Rickles modern - and they don't mesh.

Of course, the real problem is still: when is anybody going to continue the tradition of the good old American musical.