At the midpoint of the Byzantine Divine Liturgy the gifts of bread and wine are carried from the table of preparation through the body of the church to the altar, the procession called the Great Entrance, and the Cherubic Hymn is the music of that journey. The chronicle tradition of Byzantium records that the chant was introduced under Emperor Justin II, around the years 573 to 574, which makes it one of the datable landmarks of the liturgy's growth, a moment when the transfer of the gifts, once a practical necessity, was clothed in a theology. The hymn's text does something subtle, it describes the singers rather than the procession.
We who mystically represent the cherubim, it says, and who sing the thrice holy hymn to the life giving Trinity, let us now lay aside every earthly care, that we may receive the King of all, who comes invisibly escorted by the angelic hosts. The congregation is told what it has, for the moment, become, the earthly image of the angelic choirs, and what it must therefore do, put down everything else. The chant is deliberately slow, among the longest sustained pieces in the liturgy, unfolding while the clergy commemorate the living and the dead, and its unhurried motion is itself part of the meaning, earthly time set aside while the King enters.