Which Mass is assigned for which celebration is listed in the Liber Usualis (and perhaps also in the Graduale and editions of the Kyriale?). The assignment is somewhat different in the 1962 edition vs. earlier editions, because of the calendar reforms in the 50's.

These assignments are not generally thought to be strictly obligatory, though they do provide a nice variety throughout the year. There's another set of ad libitum (freely choosable) music in its own section that can be used to replace the "assigned" settings in the Kyriale.

Besides the suggestions in the Liber, there is a note on p. 78 stating that it is OK to mix and match among the Mass settings, excepting the Ferial settings. Also, the "ad libitum" chants may be used.

Isn't that in the same vein as singing the Mass of Cremation, the My Little Pony Mass, or any other Mass Ordinary setting all the time at every Mass at which music is used?

This is a side note, but: does anyone else get annoyed when people do not capitalize "Mass" when used to refer to the highest action of worship that a human can undertake?

As a victim of MDAOD (Missa de Angelis Overload Disorder) I must use caution when programming Mass VIII so we sing it once a year at Christmas time which is plenty since I have sung it or heard it at least 20,000 x in my lifetime.

We have found that this process of singing it only once a year has put us on the road to closure and healing, and as the years go by are becoming more optimistic that someday Mass VIII will not produce such visceral negative reactions.

As an antidote, we regularly comb the Kyriale for new Mass settings. Mass II is a fine choice for the Pentecost to Corpus Christi season, I think, and we really enjoyed Mass XIV for Advent and Lent. I have my eye on Mass III for the summer months. Masses V, VI and VII are great favorites with our congregation. There are moments in each that sound amazingly "modern," almost "conciliar"---e.g., the Agnus Dei from Mass VI:
(NOH accompaniment recommended. )

https://www.youtube.com/watch?v=E98cHfy8Beg

"Finally, there should be no innovation unless the good of the faithful surely demands it."

See, I'm a good Catholic in the Spirit of Vatican 2.

I meant when specifically referring to The Mass.

If the capitalization of nouns were a sound indicator of orthodoxy and piety, the Germans, who capitalize all nouns, would generally be attending church on Sundays.

This is a side note, but: does anyone else get annoyed when people do not capitalize "Mass" when used to refer to the highest action of worship that a human can undertake?

Yes! Yes! A thousand times Yes! And church instead of Church when discussing the Catholic Church!

The mass cycles in the Liber follow French traditions; I have looked at a number of sixteenth-century German graduals, and they have somewhat different cycles. For instance, since their classification of feasts is not by degree as in the Roman classification, double, semi-double, etc., but by kind, apostles, martyrs, etc., so in the German tradition Mass XI is for feasts of martyrs, Mass IV for apostles.

Since my choir sings a polyphonic mass for most solemnities, while the congregation sings the ordinary on normal Sundays, I have alternated several masses through the Sundays, Mass I for Easter, XVII for Advent and Lent, but then IV, VIII, IX, XI throughout the other seasons.

Concerning capitalization, Sacred Music follows the Chicago Manual of Style. It uses a rather "down" style, being sparing in the use of capitalization. It is admittedly a rather secular institution, but it is also an industry standard. The criterion is: the Mass as it refers to the Eucharist is capitalized, because of its close affinity with the Deity. On the other hand, mass as a composition is like symphony: Mass in B Minor, but we sang a mass by Josquin yesterday. The question of church is a question of whether it is used as a proper noun. The Catholic Church, BIshop Cordileone, but the church has bishops. The Second Vatican Council, but the documents of the council are all found online. This goes for clergy as well: Pope Francis, the pope. I realize that some of these are gray areas, but church and council are common nouns and so we use lower case, while Catholic Church and Second Vatican Council are proper nouns and in upper case.

Names of services, such as Vespers are capitalized, and so Mass as a service. But common names of genres, such as introit, are not capitalized, unless the name is that of their beginning text, Magnificat. Alleluia gives a little trouble, so I do it both ways If we refer to Alleluia by itself, it is capitalized. But with other propers, such as gradual and alleluia, I leave it lower case. This is a bit picky, but it is good to be consistent. If you are interested, you can see our style sheet on our web site

Capitalization isn't part of grammar. It's part of orthography.

But seriously: occasionally I see people making arguments about some subject or other, and using capitalization or the lack of it to make a distinction between two meanings of a word.

Such an argument is weak, because it becomes meaningless when translated into a language with different capitalization customs, or even when presented in a country with different customs.

So while I try to observe capitalization customs thoroughly (as a conservative should logically do), I don't treat other people's deviations as a moral failing.

"Lord" in all caps or small caps is standard to indicate that the Hebrew word being translated is YHWH, not Adonai. It has nothing to do with denomination.

Your question assumes that

Capitalization shouldn't be a shibboleth

implies

the rules of grammar [or orthography] are disposable

but it doesn't.

I use Chicago style for my citations, so I observe the Chicago protocol when asked to do so by my professors, and I don't tend to capitalize words like "church" or the pronouns in reference to the divine in other writing. One, it seems less prejudiced in academic papers, and two, I realized capitalizing those words gets very annoying since English usage does not capitalize every noun.