Which composer's Fourth Symphony was withdrawn after a Soviet denunciation and hidden for 25 years?

Shostakovich's. In January 1936 Pravda published an unsigned attack on his opera, headed Muddle Instead of Music, after Stalin walked out of a performance. In that climate the article was not a review but a warning, and the Fourth Symphony was pulled during rehearsals; it was not performed until 1961.

He is said to have kept a packed suitcase by the door and slept on the landing so that an arrest would not wake his children. The Fifth Symphony followed as what a newspaper called a Soviet artist's reply to just criticism - a phrase he did not write - and its triumphant ending has been argued about ever since: sincere resolution, or forced rejoicing with a gun at the back of the head.

The evidence for reading his music as coded dissent mostly comes from a memoir published after his death whose authenticity is disputed, and the argument is not settled. What is not in doubt is the pressure: he was denounced again in 1948, wrote film scores and official cantatas to stay employed, joined the Party in 1960 in circumstances his friends described as a collapse, and signed his late works with a four-note motif spelling his own initials.