 He also served as a guest conductor of the Promenade Symphony Concerts in 1942 and both the Toronto Symphony Orchestra and National Symphony Orchestra in 1943.He left Vancouver in 1944 to found the Ottawa Philharmonic Orchestra (now Ottawa Symphony Orchestra), serving as the group's first conductor through 1950.In 1952 De Ridder moved back to Vancouver where he remained until he died 13 May 1966.