Background Music During the Eucharistic Prayer?

Question: Recently, I have noticed that at some Masses background music is played during the Eucharistic prayer. Although it sometimes sounds very nice, I have difficulty hearing or understanding the priest. When did the Church allow background music to be played during the Eucharistic prayer?

Answer: The fact of the matter is that the Church does not permit any background music during those parts of the Mass said by the priest. This is one of many innovations started by those who are many times uninformed about the liturgical laws of the Church. The Church has addressed this issue many times following Vatican II as the excerpts below of documents from the Holy See demonstrate:

Musicam Sacram – Instruction on Music in the Liturgy (1967)
The use of musical instruments to accompany the singing can act as a support to the voices, render participation easier, and achieve a deeper union in the assembly. However, their sound should not so overwhelm the voices that it is difficult to make out the text; and when some part is proclaimed aloud by the priest or a minister by virtue of his role, they should be silent. (no. 64, emphasis added)

Musicam Sacram
In sung or said Masses, the organ, or other instrument legitimately admitted, can be used to accompany the singing of the choir and the people; it can also be played solo at the beginning before the priest reaches the altar, at the Offertory, at the Communion, and at the end of Mass. (no. 65, emphasis added)

Eucharistiae Participationem - Letter on Eucharistic Prayers (1973)
By its very nature the Eucharistic Prayer is the "center of the entire celebration," and "a prayer of thanksgiving and sanctification" whose purpose is "that the whole congregation of the faithful may unite itself with Christ in proclaiming the wondrous things of God and in offering the sacrifice." This prayer is offered by the ministering priest, who interprets God's voice as it is addressed to the people and the people's voice as they lift their souls to God. The priest alone should be heard, while the congregation gathered to celebrate the sacred liturgy remains devoutly silent. (no.8, emphasis added)

The General Instruction of the Roman Missal (GIRM-1975) states:
"The nature of the presidential prayers demands that they be spoken in a loud and clear voice and that everyone present listen with attention. While the priest is reciting them there should be no other prayer and the organ or other instruments should not be played."(no.12, emphasis added)

Notitiae (from 1977)_ confirms the above.
"This is a clear rule, leaving no doubt, since it is a reminder of wrong practices that have greatly impeded or diminished the people's participation in this central part of the Mass. Further, it is obvious that the organ's so-call background music often puts in the background what should be foremost and dominant. A 'background' accompaniment of the priest's homily would be out of the question: but in the Eucharistic prayer the word of the presider, Tou proestou in Justins's expression, reaches the peak of its meaning." Notitiae 13 (1977) 94-95, no. 2 (emphasis added).

Inaestimabile donum (1980)
It should be remembered that the Eucharistic Prayer must not be overlaid with other prayers or songs. When proclaiming the Eucharistic Prayer, the priest is to pronounce the text clearly, so as to make it easy for the faithful to understand it, and so as to foster the formation of a true assembly entirely intent upon the celebration of the memorial of the Lord. (no.6, emphasis added)

General Instruction of the Roman Missal (Third Typical Edition) (2002)
32. The nature of the "presidential" texts demands that they be spoken in a loud and clear voice and that everyone listen with attention. Thus, while the priest is speaking these texts, there should be no other prayers or singing, and the organ or other musical instruments should be silent. (emphasis added).

Redemptionis Sacramentum (March, 2004)
[53.] While the Priest proclaims the Eucharistic Prayer “there should be no other prayers or singing, and the organ or other musical instruments should be silent”, except for the people’s acclamations that have been duly approved, as described below. (emphasis added).
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