Task: Question Generation
Input (English): Passage: Alan Dudley Bush (22 December 1900 – 31 October 1995) was a British composer, pianist, conductor, teacher and political activist. A committed communist, his uncompromising political beliefs were often reflected in his music. He composed prolifically across a range of genres, but struggled through his lifetime for recognition from the British musical establishment, which largely ignored his works.
Bush, from a prosperous middle-class background, enjoyed considerable success as a student at the Royal Academy of Music (RAM) in the early 1920s, and spent much of that decade furthering his compositional and piano-playing skills under distinguished tutors. A two-year period in Berlin in 1929 to 1931, early in the Nazi Party's rise to power, cemented Bush's political convictions and moved him from the mainstream Labour Party to the Communist Party of Great Britain which he joined in 1935. He wrote several large-scale works in the 1930s, and was heavily involved with workers' choirs for whom he composed pageants, choruses and songs. His pro-Soviet stance led to a temporary ban on his music by the BBC in the early years of the Second World War, and his refusal to modify his position in the postwar Cold War era led to a more prolonged semi-ostracism of his music. As  a result, the four major operas he wrote between 1950 and 1970 were all premiered in East Germany.
In his prewar works, Bush's style retained what commentators have described as an essential Englishness, but was also influenced by the avant-garde European idioms of the inter-war years. During and after the war he began to simplify this style, in line with his Marxism-inspired belief that music should be accessible to the mass of the people. Despite the difficulties he encountered in getting his works performed in the West he continued to compose until well into his eighties. He taught composition at the RAM for more than 50 years, published two books, was the founder and long-time president of the Workers' Music Association, and served as chairman and later vice-president of the Composers' Guild of Great Britain. His contribution to musical life was slowly recognised, in the form of doctorates from two universities and numerous tribute concerts towards the end of his life. Since his death aged 94 in 1995, his musical legacy has been nurtured by the Alan Bush Music Trust, established in 1997.
Output (English): What is the last name of the person who wrote four major operas between 1950 and 1970?