He is noted for his trademark style of playing rapid arpeggios. His distinctive sound on the early Stranglers recordings involved the use of HohnerCembalet electric piano, Hammond L-100 electric organ, a Minimoog synthesizer, and later an Oberheim FVS-4 polyphonic synthesizer.
He also frequently contributes harmony backing vocals to the band's songs, and sang the lead vocals on a few of their tracks, including:
"Dead Ringer" and "Peasant in the Big Shitty" from their album No More Heroes
On the albums The Raven, Gospel According to the Meninblack and Aural Sculpture, Greenfield also used a Korg VC-10 vocoder. Notable instances of this include in "Genetix" when it accompanies his own vocal and during the "Gene Regulation" section underneath Hugh Cornwell's monologue, on "Baroque Bordello" towards the end of the song, and in the song "North Winds".