During the 1950s and 1960s, Austro-German scholars made decisive advances in developing concepts to account for harmonic processes in late medieval music. Despite the considerable potential these ideas hold for analysis and criticism of early music, they have hitherto exerted little influence outside their countries of origin. In order to render this valuable literature more immediately accessible to English-speaking students and scholars, this book presents translations of twelve seminal articles that originally appeared during the years 1948-1967, along with a comprehensive introductory chapter detailing the evolution of competing theories and terminology.