Those who scrutinized the historical development of Byzantine liturgical chanting could notice the late codification of this music. With the transition to the written tradition, a clear tendency to preserve orality in the new hypostasis emerged. Proto-Byzantine chanting circulated orally, this being conditioned by the original orality of the evangelical tradition. When the Eastern promoters of Christian liturgical chanting felt the need to codify the cultic repertoire, they resorted to the Ekphonetic notation, and later to the Diastematic one. Ekphonetic notation is a rudimentary notation, it has a mnemonic function, meaning the purpose of reminding the performer of a certain melodic formula that he knew before. The Diastematic notation, although it fixes several details of the melodic thread, also leaves enough room for interpretive ambiguity and can only be deciphered satisfactorily by those familiar with traditional practice. The attempt to explain the reluctance of the promoters of Byzantine religious music towards written codification will lead us to the deep roots of this art, as well as to its liturgical functionality.