This book examines the role of composers' unions in shaping cultural life under state socialism in Central and Eastern Europe. Against the backdrop of shifting political regimes, it traces how these organisations navigated ideological demands, censorship, and artistic aspirations from the late Stalinist era to the Prague Spring. Based on extensive archival research, the chapters offer insights into institutional structures, leadership strategies, and the balance between state control and artistic initiative. The volume places national case studies in broader international contexts, showing how composers' unions functioned both as instruments of power and as spaces of negotiation. Exploring their engagement with styles from socialist realism to avant-garde and popular music, the book reveals how these organisations reflected broader cultural struggles of the Cold War era and illuminates the interplay of art, ideology, and politics in societies striving to define their cultural identity.