This article studies the effect of achievements of proto-Bulgarian, Thracian, Ancient Greek and Byzantine cultures on formation of the Bulgarian nation. The main scientific concepts concerning the origins of Bulgarians, etymology of name, and matters concerning linguistic and ethnic affiliation have been analyzed. The most important historical events that bore upon formation of the Bulgarian nation have been reviewed; in particular, attention was focused upon development of religious views of Bulgarians starting from the archaic eras. Materials concerning the influence which achievements of proto-Bulgarians had on Bulgarian music and culture in general have been studied. An analysis of historical materials concerning the life of Turkish and Irano-Indian peoples, archeological cultural discoveries and accounts of various historians suggest the conclusion that archaic layers of Bulgarian folklore have relation to Irano- Indian, Turkish and Irano-Semite origins of monodic melodic culture, which were in organic contact with proto-Christian and early Christian artistic layers, thus facilitating flexible contacts with other Southern European cultural phenomena. This relation manifests itself in common features of Turkish and Bulgarian rhythms, the structure of folk music modes and the use of a quartertone system in music of these countries. One subsection systemizes historical information regarding Thracians, and offers an overview of the works of historians and scholars studying origins of the Thracian language that influenced morphological and syntactical linguistic system of Bulgarians, and religious legacy. A conclusion was drawn that Bulgaria preserved the orphic cult of Ancient Thrace no less than Greece and Byzantium did, where vocal basis of music defined exceptional originality of rhythmic structures, in particular, in instrumentalism. Accounts of Greek historians concerning secular and folk music of Thrace, rites, pantomimic scenes, etc. have been analyzed as well. The discovered sources allow to assume that practicing musicians of Ancient Thrace were prohibited from not only writing about music but even talking about it, although the myths, religious beliefs and ritual practices indicate the authoritativeness of Thracians in this particular area. Bulgaria’s inheritance of Ancient Greece’s cultural legacy, including via Byzantine Orthodoxy of the 4 th to 6 th and 9 th to 11 th centuries, as proved by numerous examples of architecture, painting art and music (and especially its rhythmical side) has been analyzed. Based on theoretical works by V. Kholopova, D. Hristov, V. Stoin and A. Stoyanov, particularities of Bulgarian “irregular rhythmics” (which have, first of all, antique metrics at its core) and the problems of their fixing have been described. Attention was also given to the hereditary features existing between Bulgaria and Byzantium, especially in religious Christian culture. The commonness manifests itself not only in the structure of Divine Service and the octoechos system but also in the monody of drone (ison) singing that remains contemporaneous in Bulgaria, in dissemination of the tradition of bass singing of psalms, in melisma which was not just an “adornment” but has retained the original rhetoric in the function of sacral mode of singing, and in the importance of ritual theatrical forms.