The frequently asked question "Why didn't Shostakovich emigrate?" reliably indicates absence of knowledge of the Soviet background.
There were three waves of emigration from the Soviet Union: (1) between 1917 and 1921, (2) during the Second World War, and (3) from 1970 to the fall of the USSR during 1989-91. While it was still possible for members of the intelligentsia to "escape" abroad in the mid-1920s, this was officially discouraged, inasmuch as the Soviet regime was by then intent on presenting itself as culturally tolerant and vibrant. (In 1930, Shostakovich's hero, the eminent and highly popular playwright Mikhail Bulgakov, begged the Central Committee to "order" him to leave the country; Stalin intervened, effectively blocking the flight of an artist whose essentially counter-revolutionary outlook he found perversely intriguing. In the same year, Evgeny Zamyatin, author of the anti-Communist allegory We and co-author of the libretto to The Nose, approached Stalin himself for leave to go abroad; the dictator left him hanging on until 1932 before granting permission. The last known individual to be allowed to leave the USSR under Stalin's dictatorship, Zamyatin spent his final years in Paris.)
By the late 1920s, so far from blithely allowing its best brains to leave the country, the Soviet government was channelling its overseas resources into the "return to the homeland" propaganda campaign, an effort to persuade émigrés (such as Gorky and Prokofiev) to come back to the USSR and join in "building Socialism". (Key figures among the émigré populace who would not play ball were often kidnapped or even assassinated.) In 1930, the Soviet Union's borders were sealed and the country went into quarantine, no further public discussion of émigré culture being permitted and all news from abroad becoming subject to total Soviet censorship (the beginning of "Soviet information space"). Anyone thereafter requesting to leave the country was charged with "anti-Soviet sentiments". (A speaker in CBC's 1994 radio series [see Centre and pseudo centre] suggests that, such was the fear within the USSR during 1936-9, that many "committed suicide or emigrated". Suicide was indeed endemic then; apart from the case of Zamyatin, emigration was inconceivable during 1930-41 and 1945-1956.)
Millions, of course, left the USSR when its borders collapsed during the war with Nazism. After the war, however, the NKVD resumed the "return to the homeland" campaign in various ways, including the notorious program of "forced repatriation" of Soviet citizens "displaced" during the conflict. Five million "returners" (vozvrashchentsy) were welcomed back to the USSR during 1945-7, many being either summarily shot for "espionage" or given 25-year sentences for "anti-Soviet activity whilst living abroad". Except for rare heroic escapes from the Gulag, there was no traffic in the opposite direction.
Following Khrushchev's "secret speech" denouncing Stalin in 1956, conditions were relaxed in a few selected cases. Otherwise, leaving the country remained extremely difficult until 1970, when pressure from Soviet Jews to be allowed to resettle in Israel caused the Brezhnev government to rethink its emigration protocols. Even so, getting out of the USSR was still difficult even as late as 1986. ("Those applying to emigrate became pariahs; they were fired from their jobs, defamed in the press, attacked and beaten in the streets, and sometimes forced to wait for their exit visas for years or to pay 'ransom' in the form of an exorbitant fee." -- Heller and Nekrich, Utopia in Power, p. 682.)
According to the widow of the late Joseph Schillinger (see Shostakovich Reconsidered, p. 184, fn. 250), Shostakovich's mother pleaded with Schillinger to do what he could to secure her son's emigration to America in autumn 1928. If true, and supposing Shostakovich to have been aware of his mother's scheming, this would constitute a fatal blow to the view (in the face of persuasive evidence to the contrary) that he was then a believing Communist. This was only months before the first RAPM attacks on his music, and uncomfortably close to the point at which Stalin moved to seal off the USSR from the outside world. Autumn 1928 would have been Shostakovich's last chance for nearly thirty years to flee abroad. The notion that he could have defected in 1949 -- during a propaganda trip to the USA, on sufferance and with his family left behind as "hostages" -- is fanciful, to say the least. Defections of this kind only became a motif of Soviet cultural delegations during the early 1960s, long after Stalin was dead. Surrounded by KGB "supervisors", Shostakovich would have had no option but to smile and go through the motions during his American trips of 1949 and 1959. Furthermore, the chances of his being allowed to emigrate in the window of opportunity of 1956-66 (see Shostakovich Reconsidered, pp. 184-5, 397) must realistically be assessed as slim to non-existent. For the Soviet Union to have stood back and let its supposed musical laureate leave the country at that time would have been a disastrous propaganda defeat. In short, the question "Why didn't Shostakovich emigrate?" is, in itself, a revealing and regrettable solecism. -- I.M.