He is best known as the keyboardist and secondary vocalist of the electronic band Orchestral Manoeuvres in the Dark (OMD), which he founded alongside lead singer and bassist Andy McCluskey in 1978.

Humphreys sang lead vocals on several OMD tracks, including the singles "Electricity", "Souvenir", "Never Turn Away", "Secret", "(Forever) Live and Die" and "What Have We Done".

Aside from his work with OMD, Humphreys fronted spin-off band the Listening Pool from 1989 to 1996, and recorded with former Propaganda singer Claudia Brücken as the duo Onetwo from 2000 to 2013.

Humphreys grew up on the Wirral Peninsula in North West England, during which time he developed an interest in German electronic music by bands such as Kraftwerk, Neu!, Can and La Düsseldorf.

Humphreys joined a variety of bands in the mid-1970s but this was mostly defined by progressive rock and it wasn't until he met Andy McCluskey that they began their own musical experiments which culminated in a one-off gig as Orchestral Manoeuvres in the Dark at Eric's Club in Liverpool.

[1][2][3] John Doran of The Quietus remarked, "If, roughly speaking, McCluskey is the intellect and inquisitive nature in [OMD], then Humphreys is the heart.

With OMD, he made use of a wide range of these including the Korg M-500 Micro Preset monophonic analog synthesizer, polyphonic analogue synthesizers such as the Sequential Circuits Prophet-5 and the Korg Trident, the electromechanical tape-sampling instrument known as the Mellotron, electronic organs such as the Vox Jaguar, and digital sampling keyboards such as the E-mu Emulator and Fairlight CMI.

On the track "Souvenir" (1981) Humphreys used recordings of a choir tuning up to create the ethereal and fluttery choral effects which gave the song its original sound.