ROME, FEB. 28, 2007 (Zenit) - Answered by Father Edward McNamara, professor of liturgy at the Regina Apostolorum university.

Q: I have recently been pondering what is necessary for valid concelebration on the part of the concelebrant. The rubrics clearly indicate that concelebrants are to recite the words extending from the epiclesis to the anamnesis, but would the omission of some component of this segment of the Eucharistic prayer compromise the offering of the sacrifice of the Mass on the part of that concelebrant? It would seem that the words of consecration are indispensable, but what of the surrounding material? -- R.H., Fulda, Minnesota

A: For a concelebrant's Mass to be valid the words of consecration recited in a low but audible voice is strictly necessary.

It is unnecessary for validity that the concelebrants recite any of the other parts of the Eucharistic prayer. But a worthy and licit celebration demands that special attention be given to those parts that should be recited by all, which thus have a certain degree of obligation.

Some parts of the Eucharistic prayer are appropriately recited alone by one concelebrant who says them with his hand extended. The principal celebrant, however, may decide to pray those parts himself for a good reason.

Nos. 216-236 of the General Instruction of the Roman Missal offer a detailed description of the words and gestures for each Eucharistic prayer. For reasons of space we quote only those numbers which refer to that which the concelebrants recite together:

"216. The Preface is sung or said by the principal priest celebrant alone; but the Sanctus is sung or recited by all the concelebrants, together with the congregation and the choir.

"217. After the Sanctus, the priest concelebrants continue the Eucharistic Prayer in the way described below. Unless otherwise indicated, only the principal celebrant makes the gestures.

"218. The parts spoken by all the concelebrants together and especially the words of consecration, which all are bound to say, are to be said in such a way that the concelebrants speak them in a very low voice and that the principal celebrant's voice be clearly heard. In this way the words can be better understood by the people.

"It is a praiseworthy practice for the parts that are to be said by all the concelebrants together and for which musical notation is provided in the Missal to be sung.

"Eucharistic Prayer I: That Is, The Roman Canon

"222. From the Quam oblationem (Bless and approve our offering) up to and including the Supplices (Almighty God, we pray that your angel), the principal celebrant alone makes the gestures, while all the concelebrants speak everything together, in this manner:

"a. The Quam oblationem (Bless and approve our offering) with hands extended toward the offerings;

"b. The Qui pridie (The day before he suffered) and the Simili modo (When supper was ended) with hands joined;

"c. While speaking the words of the Lord, each extends his right hand toward the bread and toward the chalice, if this seems appropriate; as the host and the chalice are shown, however, they look toward them and afterwards bow profoundly;

"d. The Unde et memores (Father, we celebrate the memory) and the Supra quae (Look with favor) with hands extended;

"e. From the Supplices (Almighty God, we pray that your angel) up to and including the words ex hac altaris participatione (as we receive from this altar), they bow with hands joined; then they stand upright and cross themselves at the words omni benedictione et gratia repleamur (let us be filled with every grace and blessing).

"224. At the words Nobis quoque peccatoribus (For ourselves, too) all the concelebrants strike their breast.

"Eucharistic Prayer II

"227. From the Haec ergo dona (Let your Spirit come upon) to the Et supplices (May all of us who share) inclusive, all the concelebrants speak all the following together:

"a. The Haec ergo dona (Let your Spirit come upon) with hands extended toward the offerings;

"b. The Qui cum passioni (Before he was given up to death) and the Simili modo (When supper was ended) with hands joined;

"c. While speaking the words of the Lord, each extends his right hand toward the bread and toward the chalice, if this seems appropriate; as the host and the chalice are shown, however, they look toward them and afterwards bow profoundly;

"d. The Memores igitur (In memory of his death) and the Et supplices (May all of us who share) with hands extended.

"Eucharistic Prayer III

"230. From the Supplices ergo te, Domine (And so, Father, we bring you these gifts) to the Respice, quaesumus (Look with favor) inclusive, all the concelebrants speak all the following together:

"a. The Supplices ...