Earthly worship is an imitation of heavenly praise. The earthly church at prayer unites the faithful with the prayer of the angelic praise. This thought is not simply a Byzantine theoretical supposition combined with platonic imagery, but is the vision of the Prophet Isaiah and the account of heavenly worship expressed in the fourth chapter of the book of Revelation. That the song of the church on earth is united with the praise in heaven is a theme found in the writings of many of the church fathers. St. John Chrysostom writes:

"Above, the hosts of angels sing praise; below men form choirs in the churches and imitate them by singing the same doxology. Above, the seraphim cry out in the thrice-holy hymn; below, the human throng sends up the same cry. The inhabitants of heaven and earth are brought together in a common assembly; there is one thanksgiving, one shout of delight, one joyful chorus." [1]

Byzantine mystical thought developed the idea of the angelic transmission of the chant itself. In the sixth century Pseudo-Dionysios articulated the concept of the divinely inspired "prototype"; the idea of an "intuitive divine inspiration ... in which the hymns and chants are echoes of the heavenly song of angels, which the prophets gave to the people through a sense of spiritual hearing." [2] These divinely inspired hymns and chants, which were viewed as models of the heavenly songs, serve as the foundation for all creativity. God and beauty are interrelated, and in the words of Pseudo-Dionysious:

"Divine beauty is transmitted to all that exists, and it is the cause of harmony and splendor in all that exists; like light, it emits its penetrating rays onto all objects, and it is as if it called to it everything that exists and assembles everything within it." [3]  

To read more click here (Words and Music in Orthodox Liturgical Music by Professor David Drillock)