John Clifford Farrar is an Australian music producer, songwriter, arranger, singer, and guitarist. As a musician, Farrar is a former member of several rock and roll groups including The Mustangs (1963–1964), The Strangers (1964–1970), Marvin, Welch & Farrar (1970–1973), and The Shadows (1973–1976). In 1980, he released a solo eponymous album. As a songwriter and producer, he worked with Olivia Newton-John from 1971 to 1989. He wrote her U.S. number-one hit singles: "Have You Never Been Mellow" (1975), "You're the One That I Want", and "Magic" (1980). He also produced the majority of her recorded material during that time, including her number-one albums, If You Love Me, Let Me Know (1974), Have You Never Been Mellow (1975), and her landmark studio album Physical (1981). He was a co-producer of the soundtracks for the films Grease (1978) and Xanadu (1980).