Providing music for the Traditional Latin Mass is not as hard as some believe. Below is a plan for a very simple—yet dignified & sacred—High Mass.
LET ME REMIND everyone that the full set of scores are available on the Goupil website.
As the priest processes in, the Introit is sung:
As soon as the Introit is over, the Kyrie is begun. Any Kyrie can be sung, but Kyrie IX or Kyrie X would be especially appropriate. You can find everything you need for the Mass Ordinary at this website. 1 Make sure to pick out your starting pitches before Mass begins, because there will not be time for this. Write your starting pitches directly on the score.
When the Kyrie is finished, if the priest is in the middle of the Altar, that means he’s ready to intone the Gloria. Hum the first pitches, and he will intone the words “Gloria in excelsis Deo.” Then, continue singing the rest of the Gloria. Everything that was said earlier about the Kyrie applies to the Gloria.
The priest will sing (or read) the Epistle. Follow along in the Campion Missal, and when he’s finished, sing this: Gradual & Alleluia (PDF). There are also other options for singing these. 2
When you’re finished with the Gradual & Alleluia, the priest will sing the Gospel, and he might also give a sermon. Immediately after the Sermon, he will go to the Altar and sing “Dominus vobiscum.” As soon as you reply with “Et cum spiritu tuo,” count to fifteen, and then sing the Offertory Antiphon (PDF).
It is also allowed to sing the full version of the Offertory, if the choir is capable of doing so:
You can sing some Marian pieces after the Offertory Antiphon has been sung, until the server incenses the congregation. However, any pieces sung have to be appropriate for the feast/season. The Campion Missal has Latin chants starting on page 946. There is nothing wrong with simply having silence after the Offertory Antiphon has been chanted.
After the priest sings the Preface, begin the Sanctus. Everything said earlier about the Kyrie applies to the Sanctus.
The priest will sing the Pater Noster, and you reply “sed libera nos a malo.” Then, a few seconds later, the priest will sing “Dominus vobiscum.” As soon as you say “Et cum spiritu tuo,” count to ten, and then sing the Agnus Dei. Everything said earlier about the Kyrie applies to the Agnus Dei.
After the priest turns around, elevating the Sanctissimum, he’ll say three times: “Domine, non sum dignus ut intres sub tectum meum; sed tantum dic verbo, et sanabitur anima mea.” When he’s done saying that, sing the Communion Antiphon:
After you receive Holy Communion, you can sing something, but it must match the feast/season. The Campion Missal has Latin chants starting on page 946.
After Mass, a Marian hymn can be sung, and there are tons in the Campion Missal that would work for the feast of Our Lady of Guadalupe. For example, numbers 905 through 919.
NOTES FROM THIS ARTICLE:
1 The “Ordinary” refers to Kyrie, Gloria, (Creed), Sanctus, and Agnus Dei.
2 Of course, it is also allowed to sing the Full Gradual (pdf) and the Full Alleluia (pdf), but those should only be done when a choir has rehearsed them sufficiently.