[1] He is known for his work on the Fender Rhodes electric piano and the Minimoog synthesiser, and for his percussive playing style on the Hohner Clavinet.

Hummingbird released two successful albums with Middleton as keyboard player, We Can't Go on Meeting Like This (1976) and Diamond Nights (1977), both produced by Ian "Sammy" Samwell.

In 1979, he played keyboards on Morrissey–Mullen's Cape Wrath and released Another Sleeper in the same year, an instrumental album with guitarist Robert Ahwai.

This classic jazz-funk album was released along with Cape Wrath, on Fusion Harvest/EMI Records, the duo is supported by Richard Bailey, Kuma Harada, Darryl Lee Que, Steve Gregory, Bud Beadle, George Chisholm, Trevor Barber, Chris Rainbow and some backing vocalists.

Throughout the 1980s he was also involved with Chris Rea playing on Shamrock Diaries, On the Beach, New Light Through Old Windows, The Road to Hell, Auberge, God's Great Banana Skin, Espresso Logic, La Passione, The Blue Cafe, The Road to Hell: Part 2 and King of the Beach.