Concepts of music theory

This contribution provides an overview of Middle Byzantine notation and the main theoretical concepts underlying Byzantine chant, situating them within the historical and geographical development of the liturgical-musical tradition of the Eastern Roman Empire. After outlining the origins and dissemination of Byzantine chant from the fourth century through the post-Byzantine period, the study focuses on the evolution of neumatic notation, with particular emphasis on the Middle Byzantine phase (from the mid-twelfth century), which for the first time allowed a precise representation of melodic contours and pitch relationships. The article addresses unresolved issues of interpretation, especially rhythmic aspects, highlighting the central role of oral transmission in medieval chant practice. A detailed discussion is devoted to the modal system of the oktoechos, its authentic and plagal modes, and its relationship with Western modal theory. The study further examines the principal liturgical books and chant styles—Heirmologion, Sticherarion, Psaltikon, and Asmatikon—emphasizing their melodic, functional, and stylistic features. Finally, through the case study of the thirteenth-century manuscript Messan. gr. 129, a Psaltikon–Asmatikon produced in southern Italy, the paper illustrates the palaeographical and musical characteristics of Middle Byzantine notation and underscores the importance of the interaction between written notation and oral tradition for the preservation, interpretation, and modern dissemination of the Byzantine chant repertoire.