Since the death of Pierre Boulez in 2016, the historiography of contemporary music has begun to confront the completion of one of the most remarkable careers affecting the character and context of musical life since 1945. This chapter examines the changing nature of the relationship between Messiaen and his most distinguished student. It examines Boulez’s critiques of Messiaen, and it creates a dialogue between aspects of classicism and modernism in the thinking of both composers, establishing their distinctiveness and relevance to the continuing evolution of compositional practice in the present day.