The term "Byzantine Chant" is a general one, referring to an extremely long and varied musical tradition. Its roots reach back to late antiquity and the beginning of the Byzantine Empire. Its branches today extend into all kinds of Orthodox liturgical (and secular) music around the world
As it has been for the entirety of its history, in its current incarnation Byzantine Chant is an exclusively vocal art form, without any instrumental accompaniment, and primarily and almost exclusively a melodic repertoire, consisting of a single sung melodic line, without harmonization or counterpoint.
The music of the Byzantine tradition is closely tied to its liturgical texts; indeed, it is impossible to discuss one without the other. The text of a given chant will not only determine its liturgical function, but also its musical genre and mode. In many cases, texts have been composed to mimic the poetic meter and syllabic pattern of another, in order to be sung to the exact same melody. In other cases, although their melodies are through-composed (not based on a previously existing melody), some texts are designated to be sung in a particular mode in order to evoke a certain theme or mood, most often a reference to a particularly important or popular hymn from a great feast or saint's day.
The repertoire used in the liturgical life of the Greek Orthodox Church today consists of melodies primarily from the 18th and 19th centuries which reflect musical practices in place in Constantinople as they have developed since the fall of the empire in 1453.
Byzantine Music has its own system of notation, which, like modern Western notation, has gone through successive stages of development. The form of Byzantine notation we use in liturgical music today is called the New Method, a system developed and perfected in the early 19th century during what is known as the Chrysanthine Reform. Chrysanthos of Madytos, Chourmouzios the Archivist, and Gregorios the First Cantor standardized the notational system that was in use at the time, making certain changes and refinements to facilitate accurate and standard renderings of the repertoire's structural melody. Perhaps the most valuable innovation was the creation of a system showing precise rhythmic subdivisions. Before this development, the notation was very much an aid to memory, and although it remains so in many ways, it now serves as a more specific and explicit representation of the melody.
- From the introduction of Byzantine Chant: The Received Tradition by John Michael Boyer