Which Mass?

In 1905, when the Vatican Commission on Gregorian Chant began publishing the EDITIO VATICANA—still the Church’s official edition— they assigned different Masses to different types of feasts. However, they were careful to add a note (which began with the words “Qualislibet cantus hujus Ordinarii…”) making clear “chants from one Mass may be used together with those from others.” Sadly, I sometimes worked for TLM priests who weren’t fluent in Latin. As a result, they stubbornly insisted Mass settings were ‘assigned’ to different feasts and seasons (which is false). To understand the great variety, one should examine the 1904 KYRIALE of Dr. Peter Wagner. One should also look through Dom Mocquereau’s Liber Usualis (1904), in which the Masses are all mixed up. For instance, Gloria II in his book was placed in the ‘ad libitum’ appendix in the EDITIO VATICANA.