Hartley was born in Smallfield, England, near Crawley, and was a childhood friend of future bandmate Simon Gallup. Hartley and Gallup were both members of the punk bands Lockjaw and the Magazine Spies in the late 1970s.[1] These bands often played alongside early versions of the Cure.[2]
Near the end of 1979, The Cure needed a new bassist following the departure of founding member Michael Dempsey, and recruited Gallup for the position.[3] Gallup suggested adding Hartley as the band's first full-time keyboardist to broaden their sound.[4]
Hartley was a full member of the Cure for their 1980 album Seventeen Seconds and the ensuing tour. During this period he contributed to the brief Cure side project Cult Hero.[5] He left the band later that year due to disagreements with group leader Robert Smith,[1] and dissatisfaction with the minimalist keyboard requirements in Smith's songs.[3][6]
After leaving the Cure, Hartley remained friends with Gallup and was an early member of the band that became Fools Dance. He released a solo album under the name Matthieu in 1987, and in 2005 joined the psychedelic rock band The Speak.[1]
