I read somewhere they would sing the Cherubic Hymn. This hymn is sung during the liturgy in two parts: Part one before the Great Entrance when the clergy come out from the altar with the Gifts that are to be changed into Christ's Body and Blood, Part two after the Clergy re-enter the altar area through the Royal Doors. There are many moving and hauntingly beautiful melodies for this hymn, but the words are as follows:
"Let us who mystically represent the Cherubim and chant the thrice-holy hymn to the Life-creating Trinity, now lay aside all Earthly care."
"That we may receive the King of all, who comes upborne by the Angelic Hosts. Alleluia, alleluia, alleluia."