He began playing the piano at the age of four, joining a band in Gillingham as a semi-professional, alongside peers such as Ronnie Verrell and Tommy Whittle.
[1] Greenslade arranged for Jack Jones, Chris Farlowe, Serge Gainsbourg ("Je T'Aime ... Moi Non Plus"),[3] Genesis, Cat Stevens, Diana Ross, Dusty Springfield, the Bachelors ("I Believe") and Kinderjazz.
[1] With Andrew Loog Oldham he wrote "Headlines", the B-side of "Ride on Baby" (IM 038), by Chris Farlowe, which was released in 1966.
[1][5] He collaborated with McKuen on the film scores for Joanna (1968), The Prime of Miss Jean Brodie (1969), and Scandalous John (1971).
As Bassey's musical director, from 1971 and into the early 1980s, he was the arranger and conductor of her 1970s television shows, and of the songs "Goldfinger" and "Send In the Clowns".