"I think he just wants to get us nervous," said a woman, as both the audience and the Orchestre National de France awaited the missing maestro at the Kennedy Center Saturday night.

Then, at the black-tie dinner for about 125 at the French Embassy which followed, the guests and the pa te' again arrived before the maestro, the star of the evening.

But both times, after a moment's delay, Leonard Bernstein swept in and took command. At the Concert Hall, he entered to loud applause; at dinner, salutory hugs and kisses were served up and dinner continued, conducted in harmony within the luscious decor of the embassy.

The dinner, the second this year given by the Washington Performing Arts Society's Lawyers Committee for the Performing Arts, was hosted by French Ambassador and Mrs. Franc,ois de Laboulaye. Dinner guests included Supreme Court Justices Byron R. White, John P. Stevens and Harry A. Blackmun, members of the French orchestra, Kennedy Center officials and WPAS members. Talk centered on the arts in Washington.

"There's been a lot of changes," said White. "Not in five years, but in the past 20."

"I will be very, very sad to leave," said Madame de Laboulaye, whose husband will be leaving his post in January. The de Laboulayes have spent many years here even before he was ambassador. "Twenty-five years ago this city was almost provincial," she said. "Today there is so much."

"I'm here because I love Washington, honey," said Carole Delaney, wife of committee member Edward Delaney. "I have a lot of friends in New York and 10 years from now they're going to be looking at Washington as the place."

Dinner and dessert finished, the guests turned to the ambassador, flanked at his table by Bernstein and Kennedy Center chairman Roger Stevens. "Vive la France!" exclaimed Patrick Hayes, managing director of WPAS, acknowledging the performance of the National Symphony de France and the close ties of the local arts community with the ambassador and his wife.

"Vive la France!" responded the dinner crowd. Hayes then coaxed Bernstein to the microphone.

"I thought I said it all with French music tonight," said Bernstein, almost shyly. "I come into Paris and I salute. I am extremely patriotic, I don't know why. It's like when I'm in this capital, no matter who is in the White House."

As the guests mingled, Bernstein told the story of the blood-stained score that he had used earlier in the evening: He had stabbed his hand with his baton during a rehearsal with the Orchestre National de France in Paris, the score disappeared and French police recovered it, splattered with blood. "It is not the blood of an accident, it is the blood of art and work," Bernstein said.