Agnus Dei (liturgy) Agnus Dei (liturgy) In the Mass of the Roman Rite and also in the Eucharist of the Anglican Communion, the Lutheran Church, and the Western Rite of the Orthodox Church the Agnus Dei is the invocation to the Lamb of God sung or recited during the fraction of the Host. The Syrian custom of a chant addressed to the Lamb of God was introduced into the Roman Rite Mass by Pope Sergius I (687–701) in the context of his rejection of the Council of Trullo (692), which was well received in the Byzantine East and called the Quinisext Council, but
Missa L'homme armé (Palestrina) fimus mass gave new life to work. In the Sanctus, the tenor sings the L'homme armé melody beginning on F; on the jubilant text "Hosanna," the note values are diminished such that the structural function is hidden. Agnus Dei I continues to rise to the climax which is pitched 'G'. Agnus Dei II begins as if the cantus firmus is present on "A," but proceeds to a freely composed trio. Agnus Dei III places the now-familiar tune in extremely long notes sung by the highest voice. Beginning on "A", an indication instructing the soprano to "sing without ceasing" is present,