Theology for Trads IV: The "Tridentine" Mass?

For what it's worth, I agree with Cavendish. The "Tridentine" Mass was launched on the world by Pope Pius V in 1570 and then abolished by Clement VIII in 1604.

The point to be made of course is that the liturgy changes all the time, though it ought to go without saying that change is always painful.

So, in 1570 Pius V's missal contains the following rubrical instructions:

• on entering the church the celebrant kneels and recites Introibo in domum tuam; in holocaustis reddam tibi vota mea, quae distinxerunt labia mea. (Psalm 65), then Ne reminiscaris and the five preparatory psalms;
• the Confiteor refers to "all sins" (i.e. Misereatur... omnibus peccatis; Indulgentium... omnium peccatorum);
• at High Mass the Celebrant recites Dirigatur Domine as he incenses the altar before the Introit and during the Offertory;
• at High Mass the Kyrie is said in the middle of the altar;
• the King is still included in the Canon;
• the Haec quotiescumque is said during the elevation of the chalice;
• the sermon is optional;
• the blessing at the end of Mass contained three signs of the cross, as if by a bishop.

In 1604 Clement VIII

• abolished Introibo in domum tuam and the other prayers that the 1570 Missal obliged the priest to say on entering the church;
• shortened the two prayers to be said after the Confiteor;
• directed that the words "Haec quotiescumque feceritis, in meam memoriam facietis" ("Do this in memory of me") should not be said while displaying the chalice to the people after the consecration, but before doing so;
• inserted directions at several points of the Canon that the priest was to pronounce the words inaudibly;
• suppressed the rule that, at High Mass, the priest, even if not a bishop, was to give the final blessing with three signs of the cross;
• and rewrote the rubrics, introducing, for instance, the ringing of a small bell.

In 1634 Urban VIII not only introduced his own versions of 80-90 hymns in the Roman Breviary but also

• increased the number of Signs of the Cross during the Mass from 16 to 38; and
• introduced the bowing of the head at the Holy Name, etc. 

In 1884 Leo XIII started a reverse ferret in Urban VIII's hymns, which then became a full rout under Pius X in 1911 (whose changes would eventually go into Benedict XV's 1920 missal) when the latter turned the Sundays green.

In other words, between the birth of the "Tridentine" Mass in 1570 and the Church's supposedly sudden plunge into the Bugniniverse in the 1950s, the Mass had in fact changed quite noticeably no less than four times, and each time according to the motu proprio of the Roman Pontiff.

The liturgy has precious little to do with Ecumenical Councils.

It has to do with the Pope.