Sangster played trombone with Graeme Bell and his Australian Jazz Band, later taking up the cornet and then the drums. He toured several times with Bell from 1950 to 1955, playing in Australia, the United Kingdom, Germany, Japan and Korea. In the late 1950s he began playing the vibraphone, which he found "combined the percussive qualities of the drums with the melodic capability of the trumpet" (Bisset, 1979). He played with Don Burrows in the early 1960s. Sangster formed his own quartet and experimented with group improvisatory jazz, after he became interested in the music of such musicians as Sun Ra and Archie Shepp. He rejoined the Don Burrows Group briefly in 1967 when they represented Australia at Expo 1967 in Montreal, Canada.
In 1969 Sangster began to work with rock musicians and he joined the expanded lineup of the Australian progressive rock group Tully, who provided the musical backing for the original Australian production of the rock musical Hair. He performed and recorded with Tully and their successors, Luke’s Walnut, throughout the two years he played in Hair. In 1970 he re-joined the Burrows group, this time for Expo 1970 in Osaka, Japan.