Pray Tell  reader Jeane Marie Miles writes with the latest information on the legality of troping the Lamb of God – that is, using other Christological invocations to extend the “Lamb of God” as needed to cover the liturgical action of the Fraction Rite. The  worship office in her diocese, Kansas City-St. Joseph, just received an email reply from the USCCB on the topic. 

The USCCB is aware that there is a discrepancy between the instructions in Sing to the Lord: Music in Divine Worship and instructions in the new Roman Missal on this subject. STL says at 188:

The supplicatory chant Agnus Dei accompanies the Fraction Rite. It is, “as a rule, sung by the choir or cantor with the congregation responding; or it is, at least, recited aloud. This invocation accompanies the fraction and, for this reason, may be repeated as many times as necessary until the rite has reached its conclusion, the last time ending with the words dona nobis pacem (grant us peace).” [GIRM 83] When the Agnus Dei is sung repeatedly as a litany, Christological invocations with other texts may be used. In this case, the first and final invocations are always Agnus Dei (Lamb of God).

The General Instruction of the Roman Missal says at 83:

The supplication Agnus Dei, is, as a rule, sung by the choir or cantor with the congregation responding; or it is, at least, recited aloud. This invocation accompanies the fraction and, for this reason, may be repeated as many times as necessary until the rite has reached its conclusion, the last time ending with the words dona nobis pacem (grant us peace).

The GIRM doesn’t say anything, yay or nay, about troping, which is now being interpreted to mean GIRM does not permit it.

According the USCCB official, because the new Missal is the more important document, it trumps the instructions in the USCCB document Sing to the Lord.  The USCCB will therefore have to re-write their regulations on this subject and/or revise Sing to the Lord.

Bottom line: no text other than “Lamb of God” may be used to accompany the Fraction Rite; however, that invocation may be sung more three times, if necessary, to accompany the liturgical action.