In 1991, he became a freelance engineer/producer, working with Timo Blunk (of Palais Schaumburg), Freaky Realistic,[3] TV Smith (of The Adverts) and Denim.
Since Saint Etienne re-united in the mid 1990s, Johnson has worked with the band at various times as engineer, arranger, producer[4] and live keyboard player.
He has also toured with The Syn in a line-up including guitarist Shane Theriot and drummer Alan White (of Yes), but left the band in 2006.
Johnson returned to Saint Etienne as orchestral arranger and conductor of their June 2007 live film soundtrack performance This is Tomorrow,[8] part of the celebrations which marked the re-opening of London's Royal Festival Hall after its closure for extensive refurbishment.
He has since formed The Electric Opera[10] with long-term collaborator Mark Bown, and composed for and directed numerous shows at the South London Theatre.