I have only attended the Tridentine Mass in two Churches since it was reintroduced in 2007, and I don’t know what the Church formally approves for all EF Masses. I have wondered if the practice of the congregation saying aloud the Latin responses might simply be a carryover from the practice in the OF form of the Mass. Thirty-eight years is a long time.
You are a bit confused in some of your observations, so please allow me to clarify.
The terms Tridentine Mass, EF Mass, Traditional Latin Mass all refer to the same thing. They are not different things. All of these terms refer to the pre-Vatican II Order of Mass. That Mass was indeed codified in 1570, but most of its ceremonies and texts go back much further, centuries further. After the Council of Trent the Church, in response to the Protestant Reformation, opted to standardize the liturgy. With the printing press having come into being, this was much easier to do than would previously have been the case. The Order of Mass, the way it was celebrated at Rome, became normative. All other variations, which were not necessarily huge, were suppressed, with a few exceptions. The last gospel, which previously had been recited by the priest on his way back to the sacristy, was at that time added to the Order of Mass and recited at the altar as the last prayer of the Mass. Otherwise, the texts are those used in Rome during the late Middle Ages. Between 1570 and 1965, there were occasionally very minor tweaks made, resulting in a new typical edition of the Roman Missal being issued. Most people, priests included, would be hard-pressed to identify the very minor changes made during these four centuries. The last typical edition of the 1570 missal of St. Pius V was that of 1962. The 1962 edition is the one used at all EF Masses today, be they diocesan clergy, FSSP, ICRSS, and yes, the SSPX, too.
Between 1965 and 1970 (Advent Sunday, 1969), there was a series of revisions made, and the result was an interim Order of Mass. This involved changes in language, ceremonies, rubrics and in the later changes, some textual modifications. In 1969 the new missal of Blessed Paul VI was promulgated, and it began to be used in the liturgical year 1970 (1971 in some places). This missal, including the Order of Mass, which we now call the OF, included some very substantial changes from its predecessor. The promulgation called for the missal to supersede all prior forms, “anything to the contrary not withstanding.” For all intents and purposes, this was a suppression of the EF, with some very sparing exceptions made for elderly, infirmed priests, and a special indult for priests in the UK. Only later in 2007 did Pope Benedict XVI proclaim that the old missal was, in fact, never truly suppressed. Maybe not
de jure, but it was in practice.
In 1984 St. John Paul II allowed a limited use of the 1962 missal, if the local bishop authorized it for groups who were attached to the old rite. These could not be SSPX or similar groups who impugned the validity of the OF. This was a somewhat restrictive permission, the so-called indult, and it was not granted by a large number of bishops. In the U.S. I recall about a dozen bishops permitting such Masses at the time.
However, the situation turned considerably beginning in 1988, after the excommunication of Abp. Lefebvre and the bishops that he consecrated. The Pope established the FSSP from the remnant of SSPX priests, deacons and seminarians who did not wish to follow Abp. Lefebvre into schism. The FSSP was thus a society of pontifical right, and as such, the FSSP answered to the Pontifical Commission
Ecclesia Dei, which was formed after the Lefebvre to oversee the application of the 1984 indult. The Holy Father encouraged bishops to be “generous” in granting celebrations of the EF Mass according to the indult. While by no means a landslide, celebrations of the old Mass began to steadily increase, and several other traditional communities, such as the ICRSS, were established. Diocesan celebrations slowly but steadily increased as the 1990s wore on, and the FSSP expanded to North America. Many of us were involved with licit celebrations of the EF Mass during these years, rather than waiting until 2007. That was not a year of “reintroduction,” as the post stated. It was a year of expansion, as there were already 100+ American dioceses with at least one regularly-scheduled EF Mass, prior to
Summorum Pontificum. There were even some full parishes established, including my own, formed in 1999 from an existing diocesan Latin Mass Community for the celebration of EF Masses and sacraments. So, to speak of 2007 as a year of return is not entirely accurate, as least not in many places.
Altar servers, pre-Vatican II and now, have always had to make the responses in their entirety, at EF Low Masses. At High Masses a choir was also involved with singing the responses, then and now. The Dialogue Mass movement, which began in Europe in the 1910s and moved to North America in the 1920s and 1930s, encouraged the people to make the responses at Low Masses, and even the shorter chanted responses at High Masses. In some dioceses and parishes–especially the American Midwest–this was widely promoted and practiced, while in others it was not. It varied by bishop and pastor. The Dialogue Mass movement, which had been tacitly approved by the Holy See since its earliest days, received more official support from St. John XXIII in 1958, resulting in an increased number of Dialogue Masses. However, there were still some places that lagged behind in its applications, especially those who had weak choirs. Five different levels of congregational participation were laid out by John XXIII in
De musica sacra et sacra liturgia, though the higher levels were rarely, if ever, put into practice.