The book, written on the material of the handwritten tradition, is devoted to the initial period of domestic professional music, in which its spiritual foundations were laid and the most important stylistic features were determined: wide chant, epic power and peculiar polyphony. The author reveals the process of assimilation and processing of Byzantine canons in Russia, their organic synthesis with the intonation of Russian speech culture and musical folklore.For the first time in domestic and foreign musicology, the picture of the history of temple singing of the Byzantine period in Bulgaria and Serbia is recreated, whose culture in the future turned out to be connected with Orthodoxy.The book gives a holistic view of the singing schools of Russia - Novgorod, Moscow and Usol - and highlights their most important musical features. The work provides an overview of the works and an assessment of the work of the leading chanters - Markell Bezborodogo, Fyodor Krestyanin, Ivan Lukoshkov, etc. The role of singing schools is shown in the history of early Russian polyphony. On the basis of stylistic features, a classification of the polyphony of that era is given, including lowercase, demesne and partes singing.The publication contains unique Russian, Bulgarian and Serbian chants of the 11th-17th centuries. - from the early monophony of Kievan Rus to the late polyphony of the pre-Petrine time. Samples are presented in the original notation of the Middle Ages and the author's translation into modern notation| most of them are introduced into cultural circulation for the first time.The book is intended for musicians, allied specialists - historians and culturologists, philologists and art historians, as well as for everyone who is interested in the history of Slavic art and culture.