Ferguson was also a member of local garage bands Western Union and The Red Roosters, as was Michael Fondiler.
He also held part-time jobs at different points as a theater usher and an architect's assistant for his father John Ferguson, and taught piano in a music store and studied at UCLA after high school.
Reuniting with longtime musician friends Randy California and California's stepfather Ed Cassidy, who, with Mark Andes and John Locke were in a band called the Red Roosters - Ferguson joined with them to form a jazz influenced rock group that was originally called Spirits Rebellious, after a Khalil Gibran passage.
Spirit began playing at various nightclubs and concerts in the Los Angeles area, especially the clubs along the Sunset Strip, including Whisky a Go Go.
It led to a cameo role for the band and a short speaking part in which Ferguson played a character based loosely on himself in the film Model Shop.
Matt Andes left the band after the third album and was temporarily replaced with Star Donaldson on lead guitar, and then, later, John Staehely.
While managed by Martin Pichinson, he scored a Top 10 hit with the title track on his second solo album, Thunder Island (1978), which peaked at No.9 in the US.
In 1983, his keyboards and bass were a prominent contribution to Language, a 5-track EP by acclaimed Texas guitarist Gary Myrick, who was exploring a new-wave direction at the time.
In 1982, after his sixth and last solo album, White Noise, Ferguson decided to become a soundtrack composer for movies and television.