From his student days, Boulez was fascinated by music from outside Europe, which influenced his piano writing before 1945. He describes his encounter with them as ‘decisive for [his] form of musical thought’, from Le Marteau sans maître to sur Incises, by way of Pli selon pli, Rituel and Répons. Stimulated by Cage’s works for percussion and prepared piano, he investigated timbre and rhythm, leading to new forms of writing and new conceptions of form and time; appreciation of the importance of resonant instruments, autonomous rhythmics, heterophony ensuring the fusion between harmony and polyphony, opposition between ‘striated time’ and ‘smooth time’, ritual and sacred dimensions, and ‘plastic and physical’ (Artaud’s words regarding Balinese theatre), not ‘psychological’ expression. This interest in non-European music, influenced by Messiaen and Jolivet, is part of a French tradition and distinguishes Boulez’s approach from that of most of his contemporaries in the immediate post-war period.