The first large-scale musicological publication written in the English language, published in Greece by a Greek entity (Hellenic Music Centre). The author examines the terms and conditions for the introduction of musical modernism in Greece, focusing on the early modernist works composed by Dimitris Mitropoulos in the 1920s: "Pan" (1923-24), "Aphrodite Ourania" (1924), Passacaglia, Intermezzo e Fuga (1924), 14 Invenzioni (1925), Ostinata in tre parti (1926-27), and Concerto Grosso (1928). The book is divided into three parts. The first part examines the broader political, social, and cultural context of modern Greece (1870-1940) with an analytical presentation of political history, internal and external politics and diplomacy, then moving on to the arts and letters and connecting them with the history of modern Greek music of the period. The dominance of the National School for the first half of the 20th century seems to leave little room for the collective expression of pre-war modernism, which finds autonomous artistic expressions in the works of composers such as D. Mitropoulos, N. Skalkottas, D. Levidis, G. Poneridis, and Ch. Perpessas, whose actions are concurrently examined within the cultural framework. An introductory assessment of Mitropoulos' compositional work in the 1920s leads to the second part of the study, where the aforementioned works are presented independently, chapter by chapter, under an extensive historical, analytical, and stylistic approach, featuring a wealth of documentation and evidence. The third part presents the critical recapitulation and commentary on the correspondence between Dimitris Mitropoulos and Arnold Schoenberg (1945-51), along with the original facsimiles of the 37 letters exchanged, with a dual aim: to highlight the deeper relationship between Mitropoulos and Schoenberg, and to connect the young ambitious composer of the 1920s with the mature, established, world-class maestro of the 1940s-60s.