Shostakovich -- retouched; Pages From the Life of Dmitri Shostakovich, by Dmitri and Ludmilla Sollertinsky, translated by Graham Hobbs and Charles Midgley. New York: Harcourt Brace Jovanovich. $12.95.

Any new study of this most extraordinary Russian composer must be measured against what many believe Shostakovich himself intimated in a controversial book by Solomon Volkov, published in the West in hard cover last year and just released in paperback (Harper & Row). Entitled "Testimony: The Memoirs of Dmitri Shostakovich," it purported to give the late composer's own story of his trials and frustrations in a totalitarian state, as told to Volkov, a Soviet musicologist who emigrated to the United States in 1976, the year after Shostakovich's passing.

After its publication, Shostakovich's widow and his son, still living in the Soviet Union, denounced the book as a fraud. Yet many readers believe to be authentic and to give insight into what it means to be a creative genius in a political system that would rather not allow such individuality to flower.

Dmitri Sollertinsky, a Soviet musicologist, and his wife, Ludmilla, a music critic, have written a polite, reverential, nice-guy account of the life of Shostakovich, avoiding all controversy. It is very much a Soviet-approved account, cleanly omitting any reference to personae non gratae, such as the composer's close friend and source of inspiration, cellist Mstislav Rostropovich , who left the Soviet Union and now lives and works in Washingtion, or the cellist's wife, concert singer Galina Vishnevskaya, or even Stalin, who was, after all, the key figure in so much of Soviet Russia's artistic as well as political development.

Thus, it is clear why this book was published in the Soviet Union, where some sort of account of its most illustrious 20th-century composer was needed. But for whom would an American publisher issue what amounts to a Technicolor leaflet version of this complicated, tortured life? Possibly for readers who simply must compare a Sovietized biography with what has already been published in the West. But surely not for others.

Even if one does not find the Volkov book accurate, one has only to listenm to the music to know that the Shostakovich the Sollertinskys write about and the man who wrote the late quartet, the last three symphonies, and countless other masterpieces are two entirely different people.