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.

From a prosperous middle-class background, Bush enjoyed considerable success as a student at the Royal Academy of Music (RAM) in the early 1920s and spent much of the decade furthering his compositional and piano-playing skills under distinguished tutors. A two-year period in Berlin from 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 the BBC temporarily banning his music 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 was influenced by the avant-garde European idioms of the inter-war years. He began to simplify his style during and after the war, in line with his Marxism-inspired belief that music should be accessible to the masses. 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 began to be recognised towards the end of his life, in the form of doctorates from two universities and numerous tribute concerts. Since his death in 1995, aged 94, his musical legacy has been nurtured by the Alan Bush Music Trust, established in 1997.

Bush was born in Dulwich, South London, on 22 December 1900, the third and youngest son of Alfred Walter Bush and Alice Maud, née Brinsley. The Bushes were a prosperous middle-class family, their wealth deriving from the firm of industrial chemists founded by the composer's great-grandfather, W. J. Bush. As a child Alan's health was delicate, and he was initially educated at home. When he was eleven he began at Highgate School as a day pupil, and remained there until 1918. Both of his elder brothers served as officers in the First World War; one of them, Alfred junior, was killed on the Western Front in 1917. The other, Hamilton Brinsley Bush, went into the family business and ran twice as Liberal candidate for Watford in the 1950s. The end of the war in November 1918 meant that Alan narrowly avoided being called up for military service; meantime, having determined on a musical career, he had applied to and been accepted by the RAM, where he began his studies in the spring of 1918.

At the RAM, Bush studied composition under Frederick Corder and piano with Tobias Matthay. He made rapid progress, and won various scholarships and awards, including the Thalberg Scholarship, the Phillimore piano prize, and a Carnegie award for composition. He produced the first compositions of his formal canon: Three Pieces for Two Pianos, Op. 1, and Piano Sonata in B minor, Op. 2, and also made his first attempt to write opera – a scene from Bulwer Lytton's novel The Last Days of Pompeii, with a libretto by his brother Brinsley. The work, with Bush at the piano, received a single private performance with family members and friends forming the cast. The manuscript was later destroyed by Bush.

Among Bush's fellow students was Michael Head. The two became friends, as a result of which Bush met Head's 14-year-old sister Nancy. In 1931, ten years after their first meeting, Bush and Nancy would marry and begin a lifelong artistic partnership in which she became Bush's principal librettist, as well as providing the texts for many of his other vocal works.

In 1922 Bush graduated from the RAM, but continued to study composition privately under John Ireland, with whom he formed an enduring friendship. In 1925 Bush was appointed to a teaching post at the RAM, as a professor of harmony and composition, under terms that gave him scope to continue with his studies and to travel. He took further piano study from two pupils of Theodor Leschetizky, Benno Moiseiwitsch and Mabel Lander, from whom he learned the Leschetizky method. In 1926 he made his first of numerous visits to Berlin, where with the violinist Florence Lockwood he gave two concerts of contemporary, mainly British, music which included his own Phantasy in C minor, Op. 3. The skill of the performers was admired by the critics more than the quality of the music. In 1928 Bush returned to Berlin, to perform with the Brosa Quartet at the Bechstein Hall, in a concert of his own music which included the premieres of the chamber work Five Pieces, Op. 6 and the piano solo Relinquishment, Op. 11. Critical opinion was broadly favourable, the Berliner Zeitung am Mittag correspondent noting "nothing extravagant but much of promise".

Among the works composed by Bush during this period were the Quartet for piano, violin, viola and cello, Op. 5; Prelude and Fugue for piano, Op. 9; settings of poems by Walter de la Mare, Harold Monro and W. B. Yeats; and his first venture into orchestral music, the Symphonic Impressions of 1926‍–‍27, Op. 8. In early 1929 he completed one of his best-known early chamber works, the string quartet Dialectic, Op. 15, which helped to establish Bush's reputation abroad when it was performed at a Prague festival in the 1930s.