Swainson started his career in Victoria, British Columbia, when he supported visiting American musicians such as Herb Ellis, Barney Kessell, and Sonny Stitt.

[3] Swainson has been a leading Canadian jazz player since the 1980s when he started playing with famous local and visiting acts including Tommy Flanagan, Rob McConnell, Ed Bickert, Slide Hampton, James Moody, Jay McShann, Moe Koffman, Lee Konitz, Joe Farrell, George Coleman, and Woody Shaw.

They have travelled playing all across North America, Great Britain, Europe, Australia, Hong Kong, and Japan.

They played with musicians including Joe Williams, Nancy Wilson, Diana Krall, Robert Farnon and Mel Tormé.

[3] Swainson now works at Humber College (Lakeshore Campus) as a professor in the Bass department after receiving a music degree.