 Leonard was Associate Conductor of the BBC Northern Orchestra and Assistant Conductor to Sir John Barbirolli at the Hallé Orchestra (1963-1968).In 1964, Leonard conducted the world premiere of Gian Carlo Menotti's chamber opera "Martin's Lie", at the Bath International Music Festival.From 1968 to 1973, Leonard was Music Director of the Edmonton Symphony Orchestra, where two of his orchestral compositions were premiered (an adaptation of Machaut's "Grande Messe de Notre Dame" in 1972 and "Group Questions for Orchestra" in 1973).