McGregor is perhaps best known for his foundation and leadership of The Blue Notes, a South African sextet that included collaborators Dudu Pukwana, Nikele Moyake, Louis Moholo, Johnny Dyani and Mongezi Feza. Equally as notable was McGregor's creation of the Brotherhood of Breath in 1969, which branched out from his work as The Blue Notes. The Brotherhood was a larger group than the Blue Notes, and incorporated leading English improvisors. They made several recordings throughout the 1970s, both studio sessions and live, as well as a final studio session in 1988. McGregor also released three albums of solo piano performances, and continued to be a major force in the music after leaving England to live in the French countryside. He also made a contribution to Nick Drake's Bryter Layter album by performing a piano solo on the track "Poor Boy"