The author analyses several electroacoustic works of Iannis Xenakis (Concret PH, Analogique A-B, La Légende d'Eer, Mycenae-Alpha, Gendy301 and S709) with three models: of sound material, of musical articulation and of control structure. He demonstrates how Xenakis creates a theory of sound in his electroacoustic works in the same manner as his theory of music applied in his instrumental works.