Pope Gregory I
Liturgical reforms

John the Deacon wrote that Pope Gregory I made a general revision of the liturgy of the Pre-Tridentine Mass, "removing many things, changing a few, adding some". In his own letters, Gregory remarks that he moved the Pater Noster (Our Father) to immediately after the Roman Canon and immediately before the Fraction. This position is still maintained today in the Roman Liturgy. The pre-Gregorian position is evident in the Ambrosian Rite. Gregory added material to the Hanc Igitur of the Roman Canon and established the nine Kyries (a vestigial remnant of the litany which was originally at that place) at the beginning of Mass. He forbade deacons to perform any of the musical portions of the Mass other than singing the Gospel.

Sacramentaries directly influenced by Gregorian reforms are referred to as Sacrementaria Gregoriana. Roman and other Western liturgies since this era have a number of prayers that change to reflect the feast or liturgical season; these variations are visible in the collects and prefaces as well as in the Roman Canon itself.
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