==Medieval Period==
Two concepts must be understood if we are to appreciate fully the function of music in Byzantine worship. The first, which retained currency in Greek theological and mystical speculation until the dissolution of the empire, was the belief in the [[angel]]ic transmission of sacred chant: the assumption that the early Church united men in the prayer of the angelic choirs. This notion is certainly older than the [[Apocalypse]] account ([[Book of Revelation|Revelation]] 4:8-11), for the musical function of angels as conceived in the [[Old Testament]] is brought out clearly by [[Book of Isaiah|Isaiah]] (6:1-4) and [[Book of Ezekiel|Ezekiel]] (3:12). Most significant in the fact, outlined in [[Exodus]] 25, that the pattern for the earthly worship of [[Israel]] was derived from [[Heaven]]. The allusion is perpetuated in the writings of the early [[Church Fathers]], such as [[Clement of Rome]], [[Justin Martyr|Justin]], [[Ignatius of Antioch]], [[Athenagoras of Athens]], and [[Dionysius the Areopagite]]. It receives acknowledgement later in the liturgical treatises of [[Nicolas Cabasilas]] and [[Symeon of Thessaloniki]] (''Patrologia Graeca'', CL, 368-492 and CLV, 536-699, respectively).
The effect that this concept had on church music was threefold: first, it bred a highly conservative attitude to musical composition; secondly, it stabilized the melodic tradition of certain hymns; and thirdly, it continued, for a time, the anonymity of the composer. For if a chant is of heavenly origin, then the acknowledgement received by man in transmitting it to posterity ought to be minimal. This is especially true when he deals with hymns which were known to have been first sung by angelic choirs—such as the [[Amen]], [[Alleluia]], [[Trisagion]], [[Sanctus]] and [[Doxology]]. Consequently, until Palaeologan times, was inconceivable for a composer to place his name beside a notated text in the manuscripts.
* (3)-(7) The prayers of [[Hannah]], [[Habbakuk]], [[Isaiah]], [[Jonah]] and the [[Three Holy Children|Three Children]] ([[I Kingdoms|1 Samuel]] 2:1-10; [[Book of Habbakuk|Habbakuk]] 3:1-19; [[Book of Isaiah|Isaiah]] 26:9-20; [[Book of Jonah|Jonah]] 2:3-10; Apoc. [[Book of Daniel|Daniel]] 3:26-56);
* (8) The song of the [[Three Holy Children|Three Children]] (Apoc. [[Book of Daniel|Daniel]] 3:57-88);
* (9) The [[Magnificat]] and the Benedictus ([[Book Gospel of Luke|Luke]] 1:46-55 and 68-79).
Each ode consists of an initial troparion, the [[irmos|heirmos]], followed by three, four or more [[troparion|troparia]] which are the exact metrical reproductions of the [[irmos|heirmos]], thereby allowing the same music to fit all troparia equally well.