London, 1966: Paul McCartney met a group of three electronic musicians called Unit Delta Plus. McCartney was there because he had become fascinated by electronic music, and wanted to know how it was made. He was one of the first rock musicians to grasp its potential, but even he was notably late to the party. For years, composers and technicians had been making electronic music for film and TV. Hitchcock had commissioned a theremin soundtrack for Spellbound (1945); The Forbidden Planet (1956) featured an entirely electronic score; Delia Derbyshire had created the Dr Who theme in 1963; and by the early 1960s, all you had to do was watch commercial TV for a few hours to hear the weird and wonderful sounds of the new world. The Sound of Tomorrow tells the compelling story of the sonic adventurers who first introduced electronic music to the masses. A network of composers, producers, technicians and inventors, they took emerging technology and with it made sound and music that was bracingly new.