Yesterday was Aaron Copland's 80th birthday. Mstislav Rostropovich and the National Symphony Orchestra gave a party and everyone came.

There were President and Mrs. Carter, to whom the jam-packed audience in the Kennedy Center Concert Hall gave a prolonged and warmly demonstrative ovation. There was Rostropovich, who dreamed up the whole thing. And there was Leonard Bernstein, interrupting his sabbatical year away from conducting.

It was Bernstein who led Copland onto the stage after Rostropovich opened the evening with Copland's "Fanfare for the Common Man," and who read a letter to the great composer from the president. The letter said, in part, "Wherever music is played and loved -- at home and abroad, among your fellow composers, among musicians and among ordinary listeners -- you are justly recognized as America's foremost composer . . . Rosalynn and I wish you every joy and happiness. We are proud to join in this fanfare for a most uncommon man."

Rostropovich then leaped onto the podium and conducted the orchestra and the audience in "Happy Birthday, dear Aaron!" He then enrolled Copland as an honorary member of the National Symphony, and presented him with a certificate signed by every member of the orchestra. Next came a book containing the president's letter together with greetings from Vice President Mondale and a host of Copland's musician friends across the country.

At last Copland himself stood on the conductor's stand and led "Appalachian Spring," that eternally radiant music first heard in the Library of Congress on Oct. 30, 1944. After Rostropovich conducted "El Salon Mexico," the intermission arrived with more presentations.

Morton Gould, a longtime fellow composer of Copland's, spoke on behalf of ASCAP -- the American Society of Composers, Authors and Publishers. He announced the establishment of two scholarships, given in Copland's name, for young composers studying at the Berkshire Music Center in Massachusetts and the Aspen School of Music in Colorado. Finally Leonard Silverstein, president of the NSO board of directors, read a proclamation from Mayor Marion Barry.

When Copland was finally allowed to speak, he was characteristically brief but said, with feeling, "I've had some very good evenings in my life but this is something special -- a birthday festival for me. I'm very touched and moved and I feel like a very lucky fellow."

After intermission the program continued with Rostropovich conducting "Quiet City," followed by Copland's return to lead his early, gutsy Piano Concerto, with his close friend Leo Smit as solosit. Then it was time for the "Lincoln Portrait," that extraordinary work which has been played and read before presidents and kings. Copland stood erect and red, in his firm, reedy voice, his own text and the words of Abraham Lincoln which he chose when he composed the work during World War II. Those words carried, as they have for each new generation since they were first spoken, new meaning: "Fellow citizens, we cannot escape history. We hold the power and bear the responsibility." Bernstein drew super-playing from the orchestra for what was the perfect closing to a unique evening in which lovers of music paid grateful tribute to the man who has created a part of this country's finest heritage.