The Byzantine musical system was realized progressively, it has encountered a process of evolution. It has also most certainly encountered foreign influences, but it was built like an extremely complex and complete system, a rich heritage of composed works, with a number that is difficult to specify exactly. This type of music was developed during the Roman Empire, being highly related with the development of Christianity, which had become the official religion of the Empire during the reign of Emperor Constantine, in the 4th century AD. In the development of the Byzantine repertoire we could identify three great periods: the first starting from the 3rd to the 13th century; the second, from the 13th century to the 19th century, and last but not the least, from the 19th century up to present day.
The first period is one of formation. The necessity to elaborate a Christian liturgy has been the engine of an intense poetic production called "hymnography". This great development of the poetic production has naturally led to the development of the musical art of composition, in order to use these hymns during the liturgy mass.
Oktoih is largely known as a system of the eight Byzantine modes (eight modes that we can find also in the Gregorian music, which possesses in a similar way a delimitation in four main or authentic modes, and four copied modes). The development of the eight modes' system has brought about the promotion of an eight week's liturgical cycle, each possessing its own texts or mode or, also a specificity, a special chromatic. The ongoing voice is used not only for the Vecernii and the Utrenies of Resurrection, but also during the Sunday liturgy at the Christian orthodox parishes. They offer color, a special atmosphere, to each of the eight weeks. The main accomplishment of the Byzantine Oktoih is the Anastasia, a book which contains the songs from the Vecernii and the Utrenii of the Resurrection on the eight modes. This musical work is actually attributed to Saint John Damaschin (from 750 AD). However, compositions on the eight modes (or voices) can be found in mostly all the liturgical books.
The second period is characterized by the development of the art of composition that can actually be placed voluntarily around the epoch of the so-called Master Cucuzel. He has placed a special part mostly due to the beauty of his compositions, but at the same time due to the work done in favor of the Byzantine semiography, especially by the introduction of the expression signs and of the "hironomic" signs. This Romanian master by the name of Cucuzel was born in the 12th century. This period has been marked by the major event of the fall of the Constantinople in 1453 and is usually called the post-Byzantine period. This period is marked by the remarkable development of the long songs in the callophonic style. Callophonic songs can be interpreted inside churches to give sermons a special kind of solemnity. These songs have also taken the forms of the so-called "Irmoase" and "Mathoms".
Today, Byzantine music is present only within the liturgical service of the Christian orthodox churches, where it is also called "psaltic music". Although certain autocefallic churches such as the Russian Orthodox Church, no longer use this kind of music, as it has been replaced by the choral music typical for Western societies, following a reform made by the Tsar Peter the Great, psaltic music remains a symbol of the 'teoforic' shininess of the Byzantine art. The term "teoforic" designates this art as being an ecclesiastical art that attempts to express a transcendental, divine, original and unique type of beauty.
Saint Sophia Cathedral in Istanbul is the most well-known and beautiful Byzantine monument. It has been built in the 6th century (it was inaugurated in 537) out of Emperor Justinian's desire to leave a monument to the world that may remain unique in grandeur and can keep him famous many years after his death.