I had thought that the push towards uniform congregational practice at Mass was a fruit of the latter years of Pope Pius XII, in parallel with the start of the serious reordering of the Liturgy. Read this, for example:
Method of Hearing Mass Well.
The Mass. says Père Lacordaire, is an act too sublime and holy for us to occupy ourselves with anything other than what the priest says and does. It is not the time for pious reading or private devotions. These latter cut us off from the priest, and keep the mind away from the end and object of the Holy Sacrifice.
The Mass is more than an ordinary prayer. It is a sacrifice, that is to say, a social act accomplished by the priest in the name of a body of people of whom he is the interpreter and representative. The offering is made in the name of all those who are assisting. They should therefore associate themselves with it. Several times the priest reminds them of this: at the Orate fratres, when he says "Pray, brethren, that my sacrifice and yours may be acceptable to God the Father Almighty"; at the Memento of the Living: "Be mindful of Thy servants, for whom we offer, or who offer this sacrifice to Thee". Likewise we find in the greater part of the prayers it is the plural and not the singular person which is used. The priest does not in fact say "I pray" or "I beseech" but "we pray" and "we beseech" ( quaesumus, petimus, rogamus ).
To participate in a real way in the Holy Sacrifice, the faithful should not be present simply as spectators, indifferent or distracted, but they should unite their intention with that of the priest who is offering.
The simplest and most commendable method which will be facilitated by the explanations contained in this Roman Missal, consists in associating oneself with the liturgical rites, prayers and chant of the, Mass.
The faithful follow in their Missals, at the same time as the priest at the altar is saying, the prayers of the Ordinary of the Mass, and those which are proper to the office of the day. These latter are the Introit, Collects, Epistle, Gospel, Offertory, Secret, Preface, Communion and Postcommunion. These are the ancient liturgical prayers, so beautiful and expressive, and in every way incomparably superior to the modern productions that they must assuredly be preferred to any of them. There is no necessity, however, to pay such close attention to one's book that one would scruple to raise one’s eyes to watch the movements of the celebrant at the altar; the faithful who would so act would create a sort of breach between themselves and the priest who offers the sacrifice in their names; they would be reading their Mass, but not following it.
It is much to be desired that all the faithful wherever possible should join in the singing of the chant of the Church, being careful to avoid such faults as are liable to be committed when numbers are singing together, as for instance singing loudly or drawling the melody. The singing of hymns is permitted at Low Masses but forbidden at High Masses. The Church demands that these hymns should be as much as possible in keeping with the sacrifice and the feast of the day. The Church does not approve of there being singing without a break, and forbids any voice to be raised during the most solemn part of the Mass, namely, at the Consecration.
The two characteristics of the reformers attitude to lay participation at Mass were, first, that nobody should pray anything other than the Mass: the ordinary and the propers of the particular Mass being celebrated; and second, that they should do so in unison.
The surprise to me is that this is written in a layman's hand missal which received its Nihil Obstat and Imprimatur in 1938, which means that the seeds which would grow into the crop which the reformers would reap were planted a lot earlier than I had realised.
There is another clue that the changes were being realised much earlier: in hand missals of the nineteenth century, there are extensive instructions to allow somebody attending Mass to work out what the propers for any day will be, and in the period before Pius X began the 20th Century's deep changes to the Calendar, working this out was complicated: not impossible for the average person-that's why the instructions were printed at the start of the missal; but complicated.
By the time of the 1938 Missal, laypeople are told that the rubrics are far too complicated to explain and that every Catholic should obtain a copy of the diocesan almanac for the year to find out what feasts were being celebrated. This is the first step on a path which would leak to clerical ownership of the calendar and sacred time and, consequently, the right to change it.
You would only need to be sixty to have been alive when today was the Sunday within the Octave of the Ascension; many young people today will not remember a time when the Ascension wasn't celebrated on a Sunday. I know which I prefer.