It seemed like an ideal setting for a summer concert: the South Lawn of the White House, with the First Lady in attendance, a sunny afternoon, a tree-swaying breeze, an audience of 2,000, and two accomplished youth orchestras, one from Washington, the other from Japan.

But by the end of yesterday's joint performance of the D.C. Youth Orchestra and Tokyo's Joint Philharmonic Orchestra, it seemed that only the music - written about 100 years ago by Tchaikovsky, Bizet, Suppe and Richard Strauss - had come off as planned.

The big hitch was that the audience - 2,000 children, aged to 7 to 15 - seemed more interested in seeing the famous residents of 1600 Pennsylvania Ave. NW than they were in the music.

"I want to see Jimmy Carter," said Shermonta Hailstork, 9, of 608 4th St. NW. She said that was why she had attended.

Chris Pohlhaus, 17, a cellist in the D.C. Youth Orchestra, found the concert "kind of nice." But even he was quick to add, "Jimmy Carter isn't here, though."

The difficulty of trying to keep the attention of the youngsters on a hot day was apparent from the beginning. By 2 p.m., when the concert opened with Strauss' "Don Juan," most of the listeners had converted their yellow paper programs into makeshift hats, umbrellas and fans.

Jackie Banks, 13, of 1508 Massachusetts Ave. SE., unfolded her program, made a hole in the center of it, and stuck the top of her head into the opening. "It's too hot out here to listen to some of that music," said Banks, who prefers the upbeat sound of the Silvers.

And so, by the end of "Don Juan," almost half the crowd had abandoned their folding chairs for the shade of nearby trees. An officials of the D.C. Recreation Department, who helped organize the trip declared that the show would not go on unless everyone returned to their seats.

Some did, but others just some who remained talked to their friends, especially those in the back seats where the music was barely audible.

During the performance of the final movement of Tchaikovsky's Piano Concert No. 1, Devaun Curry, 9, was playing "Slide" a modern version of "patty-cake, patty-cake," with a friend "I couldn't hear because everyone's talking," she explained.

Forty-five minutes into the program. Rosalynn Carter arrived and took a front-row seat. At the next intermission, the First Lady rose to tell the audience that the music she had heard had been "just great." And she added, "I know you all have enjoyed it."

The youngsters craned and stretched and kept quiet to see and hear her.

She gave them some news of her daughter, Amy, who is currently visiting relatives in Georgia. Amy has been playing the dulcimer and plans to take up the violin in the fall. Mrs. Carter said, adding that this concert would have proved an encouragement to her musical studies.

The musicians - 83 from Japan and 110 from Washington - were not immune from the heat and the breeze.

"It was hot and our music was blowing around. We had to play a lot by memory," said Sally Stout, the 16-year-old concertmaster of the D.C. Youth Orchestra.

Kaoru Fukuda, 21, a viola player from Tokyo, reported that he found the concert "very warm, hot."

Conductor Setsuo Tsukahara, whose ensemble is on the second leg of a 17-day tour of the United States, said the White House event had been the most exciting of the trip. "I am very, very happy."

As for the weather, Tsukahara said that he found the afternoon, "a little bit hot." But he added, "It's much better than rain."