 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).In 1971, he conducted the Edmonton Symphony in a concert featuring the British rock band Procol Harum, which was recorded and released commercially as "," although due to an apparent distaste for rock music, from the start of the project Leonard disowned any association with the performance and went so far as to refuse to have his name listed in the credits.