BBC Radiophonic Workshop – 21 was a compilation by the BBC Radiophonic Workshop to celebrate their 21st anniversary in 1979. It was compiled as an overview of their work both old and new, showcasing the changes in the Workshop as they developed from backroom sound effects suppliers for BBC Radio to full-fledged in-house music composers for the whole of the corporation. It demonstrates the move from the musique concrète and tape-manipulation techniques used in the early days, to the synthesiser works of the 1970s. The first side of the album consisted of material from 1958 to 1971, covering their early work creating jingles, sound-effects and some incidental music. This side includes the first material by Workshop founder Desmond Briscoe to be commercially released, as well as sound effects from The Goon Show, Maddalena Fagandini's interval signal that later became "Time Beat", some of Delia Derbyshire's experimental work and the pilot episode version of the Doctor Who theme music. The second side of the record covered the period between 1971–1979, including Richard Yeoman-Clark material from popular BBC series Blake's 7 and Peter Howell's vocoder heavy "Greenwich Chorus" theme for The Body in Question.