It looked like a Hollywood or Broadway premiere - massed crowds of fans, sawhorses, blue-helmeted police, celebrities running the gantlet of ''whozat?,'' and flash bulbs blinking like media lightning. But Henry James, the novelist, was quoted over the microphone, which gives you an idea of the tone.
The sixth annual Kennedy Center Honors, Washington's glittering bow to lifetime stars in the performing arts, had opened for another one-night stand. And there on the stage was master of ceremonies Walter Cronkite, introducing this year's five honorees with a line President Reagan had dropped earlier at a White House reception for them. ''Art is the shadow of humanity,'' he said, quoting Henry James, and praising the artists who ''had spent their lives casting these powerful shadows'': Katherine Dunham, the dancer; Elia Kazan, the director; Frank Sinatra, the singer-actor; James Stewart, the actor; and Virgil Thomson, the composer.
On stage, there were tributes to the artists as diverse as their backgrounds: Anthony Quinn leading a dance number from the musical ''Zorba'' for his friend Elia Kazan, an Anatolian Greek-American. Mikhail Baryshnikov, in black tie, danced ''Sinatra Suite,'' a new American Ballet Theater number choreographed by Twyla Tharp to several of ''old blue eyes's'' hits. The New York City Breakers, a group of teen-agers, performed break dancing, which nearly brought the house down, in tribute to black dance pioneer Katherine Dunham. A scene from ''The Mother of Us All,'' Virgil Thomson and Gertrude Stein's opera about Susan B. Anthony, the suffragist, was acted. And the entire US Air Corps cadet chorus, with Carol Burnett, serenaded proud pilot Jimmy Stewart.
The program will be televised over CBS Dec. 27, but viewers may not have a glimpse of the shows held before and after the broadcast. In this suddenly security-conscious city the hundreds of celebrities, politicians, and unknowns funneled through metal detectors in the center's marble lobby - the men in black tie, the women in chiffon, velvet, and taffeta gowns, whose metallic sequins and beads sometimes set off warning beeps.
After the awards, they sat down to a supper dance in the Kennedy Center's vast red-carpeted hall, transformed into a ballroom with dozens of candlelit tables decked in crimson cloths and two dozen crimson roses.
Roger Stevens, chairman of Kennedy Center, kidded, ''We gather once a year to give Art Buchwald an opportunity to make fun of the Kennedy Center deficit,'' which this year will be lightened by the half-million dollars the program will net for the center. As Walter Cronkite said, signing off for the Kennedy Center honorees: ''For the five of you, the show will always go on, for that's the way it is. . . .''