Russian-born conductor Rudolf Barshai, who was a contemporary of composers Shostakovich and Prokofiev, has died at his home in Switzerland aged 86.
He had been in ill health for some time but continued to work until the final days of his life, his agent said.
Barshai studied composition with Dmitri Shostakovich and later recorded a complete cycle of his symphonies.
He left his homeland in 1975 after Shostakovich's death and went on to conduct in London, Paris and Berlin.
In 1955, he founded the Moscow Chamber Orchestra which he led until he emigrated from the Soviet Union.
In 2000, he completed work on the orchestration of Mahler's 10th Symphony and shortly before his death, completed his arrangements on The Art of Fugue by Bach.
A spokeswoman for his agent said Barshai "considered it to be a lifetime achievement".
He also played viola as a soloist and in 1945, was a founding member of the Borodin Quartet.
"The music world has lost a true great," his agent's spokeswoman added.