The research presented in this book focuses on exploring the musical phenomenon – Giacinto Scelsi’s works for great orchestra and great orchestra with choir. The analytical issues raised by the author: construction and dramaturgy of great orchestral cycles, harmonics, time organization, Scelsian sound technique, composer’s graphic emblem as an esoteric key to his universe, oriental inspirations, numerical symbolism, extra-musical program and musical symbolism, sacrum, references to the transcendent Absolute, Plotinian correspondences and paradigms. Contextual issues: biographical aspects (chronicle of Giacinto Scelsi’s life, creative inspirations, artistic personality, evolution of musical style), sources and references (recherche sur le timbre, Orientalism and Western occult-esoteric tradition).