352. The pastoral effectiveness of a celebration will be greatly increased if the texts of the readings, the prayers, and the liturgical chants correspond as aptly as possible to the needs, the preparation, and the culture of the participants. This will be achieved by appropriate use of the many possibilities of choice described below.
Hence in arranging the celebration of Mass, the Priest should be attentive rather to the common spiritual good of the People of God than to his own inclinations. He should also remember that choices of this kind are to be made in harmony with those who exercise some part in the celebration, including the faithful, as regards the parts that more directly pertain to them.
Since, indeed, many possibilities are provided for choosing the different parts of the Mass, it is necessary for the Deacon, the readers, the psalmist, the cantor, the commentator, and the choir to know properly before the celebration the texts that concern each and that are to be used, and it is necessary that nothing be in any sense improvised. For harmonious ordering and carrying out of the rites will greatly help in disposing the faithful for participation in the Eucharist.
I. The Choice of Mass
353. On Solemnities the Priest is obliged to follow the Calendar of the church where he is celebrating.
354. On Sundays, on the weekdays during Advent, Christmas Time, Lent, and Easter Time, on Feasts, and on Obligatory Memorials:
a) If Mass is celebrated with the people, the Priest should follow the Calendar of the church where he is celebrating;
b) If Mass is celebrated with the participation of one minister only,
the Priest may choose either the Calendar of the church or his
355. On Optional Memorials,
a) On the weekdays of Advent from December 17 to December 24, on days within the Octave of the Nativity of the Lord, and on the weekdays of Lent, except Ash Wednesday and during Holy Week, the Mass texts for the current liturgical day are used; but the Collect may be taken from a Memorial which happens to be inscribed in the General Calendar for that day, except on Ash Wednesday and during Holy Week. On weekdays of Easter Time, Memorials of Saints may rightly be celebrated in full.
b) On weekdays of Advent before December 17, on weekdays of Christmas Time from January 2, and on weekdays of Easter Time, one of the following may be chosen: either the Mass of the weekday, or the Mass of the Saint or of one of the Saints whose Memorial is observed, or the Mass of any Saint inscribed in the Martyrology for that day.
c) On weekdays in Ordinary Time, there may be chosen either the Mass of the weekday, or the Mass of an Optional Memorial which happens to occur on that day, or the Mass of any Saint inscribed in the Martyrology for that day, or a Mass for Various Needs, or a Votive Mass.
If he celebrates with the people, the Priest will take care not to omit too frequently and without sufficient reason the readings assigned each day in the Lectionary to the weekdays, for the Church desires that a richer portion at the table of God’s Word should be spread before the people.
For the same reason he should choose Masses for the Dead in moderation, for every Mass is offered for both the living and the dead, and there is a commemoration of the dead in the Eucharistic Prayer.
Where, however, the Optional Memorials of the Blessed Virgin Mary or of the Saints are dear to the faithful, the legitimate devotion of the latter should be satisfied.
Moreover, as regards the option of choosing between a Memorial inscribed in the General Calendar and one inserted in a diocesan or religious Calendar, preference should be given, all else being equal and in keeping with tradition, to the Memorial in the particular Calendar.
II. The Choice of Texts for the Mass
356. In choosing texts for the different parts of the Mass, whether for the time of the year or for Saints, the norms that follow should be observed.
357. Sundays and Solemnities have assigned to them three readings, that is, from a Prophet, an Apostle, and a Gospel, by which the Christian people are instructed in the continuity of the work of salvation according to God’s wonderful design. These readings should be followed strictly. In Easter Time, according to the tradition of the Church, instead of being from the Old Testament, the reading is taken from the Acts of the Apostles.
For Feasts, two readings are assigned. If, however, according to the norms a Feast is raised to the rank of a Solemnity, a third reading is added, and this is taken from the Common.
For Memorials of Saints, unless proper readings are given, the readings assigned for the weekday are normally used. In certain cases, particularized readings are provided, that is to say, readings which highlight some particular aspect of the spiritual life or activity of the Saint. The use of such readings is not to be insisted upon, unless a pastoral reason truly suggests it.
358. In the Lectionary for weekdays, readings are provided for each day of every week throughout the entire course of the year; hence, these readings will in general be used on the days to which they are assigned, unless there occurs a Solemnity, a Feast, or Memorial that has its own New Testament readings, that is to say, readings in which mention is made of the Saint
Should, however, the continuous reading during the week from time to time be interrupted, on account of some Solemnity or Feast, or some particular celebration, then the Priest shall be permitted, bearing in mind the scheme of readings for the entire week, either to combine parts omitted with other readings or to decide which readings are to be given preference over others.
In Masses for special groups, the Priest shall be allowed to choose texts more particularly suited to the particular celebration, provided they are taken from the texts of an approved Lectionary.
359. In addition, in the Lectionary a special selection of texts from Sacred Scripture is given for Ritual Masses into which certain Sacraments or Sacramentals are incorporated, or for Masses that are celebrated for certain needs.
Sets of readings of this kind have been so prescribed so that through a more apt hearing of the Word of God the faithful may be led to a fuller understanding of the mystery in which they are participating, and may be educated to a more ardent love of the Word of God.
Therefore, the texts proclaimed in the celebration are to be chosen keeping in mind both an appropriate pastoral reason and the options allowed in this matter.
360. At times, a longer and shorter form of the same text is given. In choosing between these two forms, a pastoral criterion should be kept in mind. On such an occasion, attention should be paid to the capacity of the faithful to listen with fruit to a reading of greater or lesser length, and to their capacity to hear a more complete text, which is then explained in the Homily.
361. When a possibility is given of choosing between one or other text laid down, or suggested as optional, attention shall be paid to the good of participants, whether, that is to say, it is a matter of using an easier text or one more appropriate for a given gathering, or of repeating or setting aside a text that is assigned as proper to some particular celebration while being optional for another, just as pastoral advantage may suggest.
Such a situation may arise either when the same text would have to be read again within a few days, as, for example, on a Sunday and on a subsequent weekday, or when it is feared that a certain text might give rise to some difficulties for a particular group of the Christian faithful. However, care should be taken that, when choosing scriptural passages, parts of Sacred Scripture are not permanently excluded.
362. The adaptations to the Ordo Lectionum Missae as contained in the Lectionary for Mass for use in the Dioceses of the United States of America should be carefully observed.
363. In any Mass the orations proper to that Mass are used, unless otherwise noted.
On Memorials of Saints, the proper Collect is said or, if this is lacking, one from an appropriate Common. As to the Prayer over the Offerings and the Prayer after Communion, unless these are proper, they may be taken either from the Common or from the weekday of the current time of year.
On the weekdays in Ordinary Time, however, besides the orations from the previous Sunday, orations from another Sunday in Ordinary Time may be used, or one of the Prayers for Various Needs provided in the Missal. However, it shall always be permissible to use from these Masses the Collect alone.
In this way a richer collection of texts is provided, by which the prayer life of the faithful is more abundantly nourished.
However, during the more important times of the year, provision has already been made for this by means of the orations proper to these times of the year that exist for each weekday in the Missal.
The Eucharistic Prayer
364. The numerous Prefaces with which the Roman Missal is endowed have as their purpose to bring out more fully the motives for thanksgiving within the Eucharistic Prayer and to set out more clearly the different facets of the mystery of salvation.
365. The choice between the Eucharistic Prayers found in the Order of Mass is suitably guided by the following norms:
a) Eucharistic Prayer I, or the Roman Canon, which may always be used, is especially suited for use on days to which a proper text for the Communicantes (In communion with those whose memory we venerate) is assigned or in Masses endowed with a proper form of the Hanc igitur (Therefore, Lord, we pray) and also in the celebrations of the Apostles and of the Saints mentioned in the Prayer itself; likewise it is especially suited for use on Sundays, unless for pastoral reasons Eucharistic Prayer III is preferred.
b) Eucharistic Prayer II, on account of its particular features, is more appropriately used on weekdays or in special circumstances. Although it is provided with its own Preface, it may also be used with other Prefaces, especially those that sum up the mystery of salvation, for example, the Common Prefaces. When Mass is celebrated for a particular deceased person, the special formula given may be used at the proper point, namely, before the part Remember also our brothers and sisters.
c) Eucharistic Prayer III may be said with any Preface. Its use should be preferred on Sundays and festive days. If, however, this Eucharistic Prayer is used in Masses for the Dead, the special formula for a deceased person may be used, to be included at the proper place, namely after the words: in your compassion, O merciful Father, gather to yourself all your children scattered throughout the world.
d) Eucharistic Prayer IV has an invariable Preface and gives a fuller summary of salvation history. It may be used when a Mass has no Preface of its own and on Sundays in Ordinary Time. On account of its structure, no special formula for a deceased person may be inserted into this prayer.
366. It is not permitted to substitute other chants for those found in the Order of Mass, for example, at the Agnus Dei (Lamb of God).
367. In choosing the chants between the readings, as well as the chants at the Entrance, at the Offertory, and at Communion, the norms laid down in their proper places are to be observed (cf. nos. 40-41, 47-48, 61-64, 74, 86-88).
 Cf. Second Ecumenical Council of the Vatican, Constitution on the Sacred Liturgy, Sacrosanctum Concilium, no. 51.
Missale Romanum, Ordo lectionum Missae, editio typica altera, 1981, Praenotanda, no. 80.
Missale Romanum, Ordo lectionum Missae, editio typica altera, 1981, Praenotanda, no. 81.