This volume, arising from the three-year work of a research group funded by the Ernst von Siemens-Musikstiftung, consists of monographic studies on the conception of harmony in the works of Béla Bartók, Claude Debussy, Paul Hindemith, Arnold Schoenberg, Aleksandr Nikolaevič Scriabin, Igor Stravinsky, Edgard Varèse and Anton Webern. The authors focus their attention on one or more works by the composer under consideration, relating harmonic processes to the theoretical issues debated at the time or emerging in the subsequent decades. The structure takes particular account of current developments in international musicology, of the gaps present in Italian scholarship, and of the needs of higher-level teaching in AFAM and university institutions. At the same time, it aims to contribute to contemporary reflection on, and methodology in, music theory. The editor’s introductory essay illustrates the historical methodology adopted in the book: the harmonic techniques of the individual composers are placed within the theoretical horizon of their time and, in certain cases, elucidated in the light of the composers’ own reflections.