This chapter focuses on the use of spatial technique in key works that span a great deal of Pierre Boulez’s career: Poésie pour pouvoir (1958) for orchestra and tape, Domaines (1968) for clarinet and ensemble, Rituel in memoriam Bruno Maderna (1974–5) for orchestra in eight groups and Répons (1981) for six soloists, live electronics and ensemble. These works are then compared with spatialised instrumental music by his contemporaries, Karlheinz Stockhausen, Karel Goeyvaerts, Iannis Xenakis and Luigi Nono, which will shed light on Boulez’s specific approach to this artistic practice. Boulez’s unique contribution to the history of spatialisation lies in the strong articulatory function he ascribed to this performance practice. He created a typology of sonic movements that clarify the structural relationships of his spatialised works.