Williamson was born in Sydney and studied at the conservatory there with Eugene Goossens. In 1950 he moved to London where he worked as an organist, a proofreader, and a nightclub pianist. From 1953 he studied with Elisabeth Lutyens.
Williamson was a very prolific composer at this time, receiving many commissions. He often performed his own works, both on organ and piano.
In 1975, the death of Arthur Bliss left the title of Master of the Queen's Music vacant. As the preeminent British composer of the time, Benjamin Britten was the obvious choice to replace him, but he was very ill, and so, to the surprise of many who expected a better known composer such as Michael Tippett to take the post, the title went to Williamson. Williamson was the first non-Briton to hold the post.
Although Williamson wrote a number of pieces connected to his royal post early in his tenure, such as Lament in Memory for Lord Mountbatten of Burma (1980), this dropped off for the last twenty years or so of his life. Indeed, his compositional output as a whole slowed considerably due to a series of illnesses. He died in 2003 in a hospital in Cambridge.
Some of Williamson's early works use the twelve tone technique of Arnold Schoenberg, but his greatest influence is often said to be Olivier Messiaen. He discovered Messiaen's music shortly before converting to Roman Catholicism in 1952. He was also influenced by Britten, as well as jazz and popular music (this latter influence may have come in part from him working as a night club pianist in the 1950s).
Williamson wrote seven symphonies, four piano concertos, operas including Our Man in Havana and The Violins of Saint Jacques, the ballet Sun Into Darkness, choral works, chamber music, music for solo piano, music for film and television, and others.
Williamson also wrote music for children, including the opera The Happy Prince (based on the story by Oscar Wilde) and cassations, short operas incorporating audience participation. One of these, The Valley and the Hill, written for the silver jubilee of Elizabeth II, was performed by 18,000 children.
Williamson became much less prolific in later life, although continued to write occasionally, with the orchestral song cycle on texts by Iris Murdoch A Year of Birds premiered at the Proms in 1995.
Despite Williamson's relatively accessible melodic style, his pieces are rarely performed or recorded.Williamson's music