Soviet physicist and Nobel Peace Laureate Andrei Sakharov, who will be 60 tomorrow, is now in exile in Gorki. Last night his birthday was marked by a concert and speeches in the Kennedy Center.

The musicians among those marking the occasion were the 18 members of the Soviet Emigre Orchestra, 13, of whom were described as having been "in bondage four years ago in the Soviet Union." Today they play under the direction of Lazar Gosman, who, with his wife and son, left the Soviet Union in 1977. He is now associate concertmaster of the St. Louis Symphony.

These skilled musicians played Mozart's "Eine Kleine Nachtmusik" in a quiet manner. But when they turned to Gosman's excellent arrangement of the Eighth String Quartet of Shostakovich, they became inspired by the autobiographical despair that marks nearly every page of the music. It is filled with echoes of earlier works written when the composer, at 19, had not yet come to know the bitterness of political oppression and coercion against which he fought for most of his adult life. It is music of immense emotive power that evoked strong and expressive playing.

The 11 speakers included Sen. Edward Kennedy (D-Mass.), who expressed the dominant mood of the evening when he said, "Sakharov has been sent to Gorki but no exile can silence his shining example or his soaring hopes." Rep. Millicent Fenwick (R-N.J.) spoke with such eloquence of Sakharov as "the voice of the conscience of mankind" that the audience rose to its feet with prolonged applause when she finished.

There were also greetings from President Reagan, Alexander Solzhenitsyn and Mstislav Rostropovich. It was an occasion on which far more was felt than could be put into words.