In all historical times music was regarded as a supreme art allowing for the best expression of religious feelings. It has been and will remain the most intelligible language for prayer communion between God and man. As early as the ancient times, the pagan religious cults have exploited the miraculous impact of the art of music on the souls of worshippers during religious rites and sacrifices. The Christian religion has also introduced music as an integral constituent of the worshipping service. Following the example of Jesus Christ, who sang out loud at the Last Supper with the Holy Apostles, the Christian Church, from the very beginning of its existence has established and canonised vocal music as the most suitable manner of temple performance, resting on the conviction that human voice is the most perfect musical instrument.
The theory of Eastern Church chants (which are still employed by the Orthodox Church) was set up by St. John of Damascus in the 7th century. From the multiple religious hymns performed by the various Christian communities, St. John of Damascus chose only those which he thought most suitable for the uniform use by the Church and compiled the so called Vocal Eight-Part Chants Book, which is still in use by the Orthodox Church. The OCTOICH by St. John of Damascus is strictly defined within certain limits which restrict melody variation. Bulgaria adopted Christianity as its official religion in 865. About the same time, the brothers St. Cyril and St. Methodius created the Slavonic alphabet (the Cyrillic alphabet), which allowed for religious scriptures to be translated into the Slavonic languages, whereupon services began to be performed in the language of everyday use. These events served as the impetus of a tremendous cultural and political bloom, which continued for the following two centuries. The development of Eastern Orthodox