Last night, the National Gallery of Art's East Building was transported in imagination to the Japan of another era, a time before Toshibas and Toyotas, trades and treaties, before Japan was an industrial samurai.

And from this land and time when all life and even death was an arcane art, J. Carter Brown revealed, in a speech so ornamented with flowery phrases it sounded as though it had been calligraphed with a Japanese brush, will come the great museum exhibition of 1988.

Beginning Oct. 30, 1988, the National Gallery of Art will exhibit 450 rare Japanese artworks from the Daimyo (translated as "great named landholdings") culture of 1200-1800.

The exhibit will include at least 160 rare objects classified by the Japanese as National Treasures, Important Cultural Properties and Important Objects. Among them are portrait paintings and sculptures; feudal armor, swords and saddles; scrolls and calligraphy; architectural devices such as panels, screens and sliding doors; table settings, including lacquer, ceramics and tea utensils of various materials; textiles; and from the theater, Noh masks and musical instruments and even a real teahouse of the October moon, complete with Japanese tea masters and antique tea services, as well as a series of Noh plays.

The exhibit, Brown says, will be shown only in Washington.

Last night, 250 or so fortunate guests had a small glimpse, a taste, a teaser of what is to come:

The music, so strange, so distant, as if made by the passage of a star in some unknown celestial system ...

The dance, a ritual warfare, an elaborate presentation of spears and daggers and fearful stances as if to exorcise violence itself ... The food, delicate morsels from an older time and taste ...

The honored guests, Japanese Crown Prince Akihito and Crown Princess Michiko, who greeted other guests with a quiet, almost shy charm, but made so much effort to be friendly that both Japanese and Americans were amazed ...

The entertainers, performers of gagaku, dance and music from the 9th century, brought from the Court of the Chrysanthemum Throne itself.

At the party, after their imperial majesties had left, Brown said, "We had wanted a Japanese exhibit for years. But it was so hard to arrange, because they put the brakes on the lending of their rarities. We have had only one Japanese exhibit in my time, the Noh robes. Finally a few years ago the Japanese sent a show of art of the Edo period to London. I said, 'Let's have that one.' But they said, 'Oh no, we want to send something better to the United States.'

"So finally, after working for three or four years, we put it together. And then it became a matter of great government excitement, and they kept urging us to take more artworks -- pieces we hadn't dared to ask for because they were so precious. And then last year, I was at a party given by the Japan Foundation, and I learned their imperial highnesses were coming here this week, so I thought, what a wonderful time to make the announcement."

Almost lighting up at the thought, Brown promised, "It will be as great as the 'Treasure Houses of Britain.' "

Brown took the crown prince and princess through the East Building, where the exhibit will be installed on multiple floors. In return, the princess, with a gentle nod of her diamond hair comb, gave him a verbal tour of the performance of the gagaku, whispering explanations in soft, fluent English as the magnificent dancers, in helmets, bonnets, trains, kimonos and pantaloons, all richly ornamented with royal designs, performed.

U.S. Ambassador to Japan Mike Mansfield told the heirs to the Japanese throne and the other guests that he is impressed with the speeches the crown prince has made on this trip, because he seems to have a "better understanding of problems we have with each other in trade. Misunderstandings arose because Americans lack patience and speed is not a Japanese virtue. Our interdependence makes our bilateral relationship the most important one we have. And as the world moves into the century of Asia, we must remember we have more in common than differences."

The differences last night looked very small. Bill Holman, partner in Design Cuisine, which catered the reception, said he learned how to do many of the exotic medieval dishes served at the party on his trip two years ago to Japan. Washington developer Frank Saul and his wife Elizabeth said they were just back from Japan, by way of Kashmir.

The guests also included Sen. Mark Hatfield and Milo Beach, acting director of the new Smithsonian Center for Asian Art, who said he hopes to have Asian music programs in the Freer. And of course, representatives of the exhibit's corporate sponsors: R.J. Reynolds Co. Washington chief Paul Bergson, whose company hopes to sell cigarettes in Japan now that some trade barriers have been torn down; and Suetaro Kawakami of Yomiuri Shimbun, Japanese sponsor with the Nomura Securities Co. Ltd. The National Gallery is collaborating with Japan's Agency for Cultural Affairs and the Japan Foundation to bring the show over.