The council sets guidelines for the use of the vernacular, first for the readings and the prayers of the faithful. Second would be portions of the Mass in which the people say or sing their part.
In Masses which are celebrated with the people, a suitable place may be allotted to their mother tongue. This is to apply in the first place to the readings and “the common prayer,” but also, as local conditions may warrant, to those parts which pertain to the people, according to the norm laid down in Art. 36 of this Constitution.
The Mass ordinary should be known in Latin. By the people. Not just the choir.
Nevertheless steps should be taken so that the faithful may also be able to say or to sing together in Latin those parts of the Ordinary of the Mass which pertain to them.
The presumption seems to be that the council bishops don’t expect the people to know them. This would also seem an argument against the use of a choir-only Mass setting. The bishops have the clear expectation that the people should participate vocally, by either speech or song.
And wherever a more extended use of the mother tongue within the Mass appears desirable, the regulation laid down in Art. 40 of this Constitution is to be observed.
Article 40 refers to more radical cultural or missionary adaptations.