Hyde is well known for providing lead vocals for Underworld. He founded the group along with Rick Smith.

Karl had a pop band, the Screen Gemz and badgered Rick Smith into joining whilst at Cardiff art college. In 1983 they recorded two albums for CBS Records International with a proto-electroclash, new romantic band, whose name was a graphic squiggle, which was soon given a pronunciation, Freur. Freur disbanded in 1986.