Swedish trombonist Eje Thelin (1938-1990) and Dutch trombonist Willem van Manen (1940). They were forerunners on this instrument within the European improv-music that distinguished itself from the American tradition. Recordings from 1969 and 1979.
Sources:
Eje Thelin Graz 1969 (Dragon 377)
Willem van Manen (BVHaast 027)
