Reading this on Zenit made me think of my own parish:
ROME, JULY 13, 2004 (Zenit.org).- Answered by Father Edward McNamara, professor of liturgy at the Regina Apostolorum Pontifical University.
Q: It is common in my diocese for priests, after the Lamb of God, when the Missal reads “This is the Lamb of God, who takes away the sins of the world …” to substitute a different (but still true) title or description of Christ – usually related to the Gospel of the day. For example, “This is Jesus, who today calls us to take up our cross and follow him …” Is this permitted? – C.S., Hamilton, New Zealand
A: The short answer to this, and to other similar questions regarding priests altering prescribed texts or composing new ones, is no.
But – and there is a but – in some countries and religious congregations, small additions have been made to these prayers with proper authorization from the Holy See.
Our choirs have added an extra line – “Have mercy on us” X 3, followed by one “Grant us Your peace”. BUT they only sing “O Lamb of God” once. The other three times they use other descriptions of our Lord.
I’m wondering if this kind of alteration is wide-spread or if we’re merely an anomaly.