Catholic Encyclopedia (1913)/Chapter and Conventual Mass
As a general rule, churches in which the Divine office is to be said publicly every day must also have Mass said daily. This Mass is the "conventual" Mass (missa conventualis); it completes, with the canonical Hours, the official public service of God in such a church. A conventual Mass then is to be sung or said in all cathedrals and collegiate churches that have a chapter; in this case it is often called the "chapter" Mass (missa capituli), though the official books constantly use the general name "conventual" for this Mass too. A conventual (not chapter) Mass must also be celebrated daily in churches of regulars who have the obligation of the public recitation of the office, therefore certainly in churches of monks and canons regular. Whether mendicant friars have this obligation is disputed. Some authors consider them obliged by common law, others admit only whatever obligation they may have from their special constitutions or from custom. Some extend the obligation even to churches of nuns who say the office in choir. That friars may celebrate a daily conventual Mass according to the rule of monastic churches is admitted by every one (de Herdt., I, 14). A chapter Mass then is a kind of conventual Mass, and falls under the same rules.
The obligation of procuring the conventual Mass rests with the corporate body in question and so concerns its superiors (Dean, Provost, Abbot, etc.). Normally it should be said by one of the members, but the obligation is satisfied as long as some priest who may celebrate lawfully undertakes it. The conventual Mass should always, if possible, be a high Mass; but if this is impossible, low Mass is still treated as a high Mass with regard to the number of collects said, the candles, absence of prayers at the end, and so on. It may not be said during the recitation of the office, but at certain fixed times between the canonical Hours, as is explained below. The general rule is that the conventual Mass should correspond to the office with which it forms a whole. It is not allowed to sing two high Masses both conformed to the office on the same day. On the other hand, there are cases in which two different conventual Masses are celebrated. The cases in which the Mass does not correspond to the office are these: on Saturdays in Advent (except Ember Saturday and a Vigil), if the office is ferial the Mass is of the Blessed Virgin. On Vigils in Advent that are not also Ember days, if the office is ferial the Mass is of the Vigil commemorating the feria. On Maundy Thursday and Holy Saturday the Mass does not conform to the office. On Rogation Tuesday, if the office is ferial the Mass is of Rogation. On Whitsun Eve the office is of the Ascension, but the Mass a Whitsun Mass. When a Vigil, an Ember day or Rogation Monday falls within an octave (except that of the Blessed Sacrament) the office is of the octave, and the Mass of the feria commemorating the octave. Except in Advent and Lent, on Ember days, Rogation days and Vigils, if the office is ferial and the Sunday Mass has already been said that week, the conventual Mass may be one of the Votive Masses in the Missal appointed for each day in the week. Except in Advent, Lent and Paschal time, on the first day of the month not prevented by a double or semi-double, the conventual Mass is a Requiem for deceased members and benefactors of the community.
On doubles, semi-doubles Sundays, and during octaves, the conventual Mass is said after Terce, on simples and ferias after Sext, on ferias of Advent and Lent, on Vigils and Ember days after None. There are also occasions on which several conventual Masses are said on the same day. On ferias of Lent, on Ember days, Rogation days and Vigils when a double or semi-double occurs, or during an octave or when a Votive office is said, the Mass corresponding to the office is said after Terce, that of the feria after None. On Ascension eve, if a double or semi-double occurs, the Mass of the feast is said after Terce, that of the Vigil after Sext, that of Rogation after None. In the case of the conventual Requiem mentioned above, if a simple occurs or if the Mass of the preceding Sunday has not yet been said, the Requiem is celebrated after the Office of the Dead, or if that is not said, after Prime, the Mass of the simple or Sunday after Sext. On All Souls' day (2 Nov.) the Mass of the octave (or feast) is said after Terce, the Requiem after None. When an additional Votive Mass has to be said (for instance for the Forty Hours or for the anniversary of the bishop's consecration or enthronement, etc.) It is said after None. On the Monday of each week (except in Lent and Paschal time) if the office is ferial the conventual Mass may be a Requiem. But if it is a simple or a feria with a proper Mass, or if the Sunday Mass has not been said, the collect for the dead (Fidelium) is added to that of the day instead. These rules concerning the celebration of two or more conventual Masses apply as laws only to chapters. Regulars are not bound to celebrate more than one such Mass each day (corresponding always to the office), unless the particular constitutions of their order impose this obligation.
See the Rubrics of the Missal (Rubr. gen. tit. I-VII), where the Mass in question is primarily the conventual Mass, and any authorized book of ceremonial; DE HERDT, S. Liturgi Praxis (Louvain, 1894), 14-17; LE VAVASSEUR, Manual de Liturgie (10th ed., Paris, 1910), 205-221; DALE, Ceremonial according to the Roman Rite (London, 1906).