In 1983, Campbell developed an overwhelming interest in world music and spent most of the next decade-and-a-half mastering a wide variety of wind instruments, harps and lutes from diverse cultures around the world. This led to an ongoing career as a specialist session musician and composer for films, theatre and television, including work with the Royal Shakespeare Company and contributions to "The Last King of Scotland", "Long Walk to Freedom", "Harry Potter and the Goblet of Fire", "State of Play", the 2008 revival of "Survivors" and the 2017 film of "The Mummy". He has enjoyed a run of cinema collaborations with his 1970s creative partner David Anderson, including "Dreamland Express", "In the Time of Angels" and "Deutsche Post".