The 104-member National Symphony Orchestra will perform a concert on the White House lawn Oct. 6 at a reception President and Mrs. Carter will give for Pope John Paul II. Nearly 5,000 people have been invited.

Rosalynn Carter made the announcement yesterday at a reception for the symphony's board of directors. "We wanted something appropriate," she said later of the decision to invite the National Symphony, conducted by Maestro Mstislav Rostropovich.

The Russian-born Rostropovich hailed the occasion as "a very great honor for me and for the orchestra. I'm very, very happy about it."

Rostropovich said he has selected music he believes to be "very close to the United States."

Selections will be William Schuman's "American Festival Overture" and Dvorak's "New World Symphony," he said.

Austin Kiplinger, president of the NSO board of directors, said that in addition to the works by an American composer and a Czech (Dvorak) who composed in America, there also will be a Polish Polonaise "especially for the pope."

Kiplinger said Rostropovich originally thought of playing something by Tchaikovsky, when planning began for the outdoor White House concert.

"Then he thought to himself," Kiplinger explained, "'Here I am a Russian and I elect to play a Russian composer. No, that's not right. I'll play Dvorak.'"

Kiplinger, who had been involved in arrangements between the White House and the symphony, said there had been some logistical problems to work out.

The permanent outdoor stage, situated on the western half of the South Lawn, was thought to be poorly positioned since it would be behind the audience, Kiplinger said. Plans have been made to move it closer to the South Portico, west of a platform on which the president and the pope will stand.

The schedule for the Oct. 6 reception calls for the orchestra to perform for an hour as the nearly 5,000 guests gather on the South Lawn. The pope and his host, meanwhile, will be meeting inside the White House both at a private reception and later in the Oval Office. They will greet the crowd at approximately 3:45 p.m. The pope will depart around 4:20 p.m.

The pope will arrive at the White House on Oct. 6 at 1:30 p.m. where he will address a crowd of 1,000 members of Congress, the Judiciary, the Cabinet, the White House staff and their families assembled on the North Lawn.

Rostropovich said he had not met the pope -- "I only congrulated him with a telegram when he was elected pope" -- and that he did not know what kind of music the pontiff likes.

"But I think it is probably heavenly music."

As members of the NSO group formed a line to shake hands with Rosalynn Carter, Rostropovich discussed the latest defection by two Soviet citizens, Olympic gold medal figure skaters Ludmilla Belousova and Oleg Protopopov.

He said he looks forward to the day when Soviet citizens who leave their country "will no longer be something special -- if people keep running, it will force them (the government) to change."

Rostropovich, who made his American conducting debut with the National Symphony in 1975, said the human rights agreement of the Helsinki accords which the Soviet Union signed "states very clearly that a person has a right to choose his own place of living or working.

"So whoever stays in the West in order to work for the greatness of Russian art or Russian sports, whatever the form of art, can't be called betrayers, nor their families who stay behind in the Soviet Union be treated as families of betrayers."

Rostropovich said he never defected from the Soviet Union -- "They threw me out and deprived me of the opportunity to return by depriving me of citizenship." He said authorities there continue to "take revenge" upon his sister Veronica, a musician, by prohibiting her from touring abroad with her orchestra.