Conductor Mstislav Rostropovich credits recent Soviet moves toward artistic freedom for his plan to present the world premiere of a long-suppressed musical satire written by the late composer Dmitri Shostakovich to ridicule the Stalinist regime.

The unpublished, 15-minute theatrical piece entitled "Rayok," Russian for "Little Eden," will be performed for the first time Thursday night in the Kennedy Center Concert Hall, with Rostropovich at the piano leading a cast of four bass singers and a small mixed chorus.Three additional performances will be given at the Kennedy Center through Tuesday, and Shostakovich's son, Maxim, a conductor who defected to the United States in 1981, was expected to be in the audience for a Sunday afternoon performance in New York's Carnegie Hall.

Rostropovich, the Soviet-born music director of the National Symphony Orchestra, apparently acquired a copy of the score and libretto for "Rayok" only recently. He refused to say how or exactly when it fell into his hands.

"There are a lot of counterfeits around," he said, "but I'm willing to put my life on the line that this is Shostakovich's music."