A more important question is the relation of the “Tridentine” liturgy to its predecessors. The historical context of its emergence is: flourishing local liturgies, the destructive liturgical movements of the Renaissance, and the confusion caused by the Protestant Revolt. In this situation, the Council of Trent had to restore order and — at least according to its desire — return to the pristine Roman tradition as was clearly explained in the introduction to the Missal. The restoration or return had two components: the approval of all cathedral or monastic liturgies that had existed from time immemorial while removing some of their excesses; and secondly the proposal of a new exemplary Roman rite, originally only intended for those who did not possess a venerable, ancient, and basically Roman cathedral liturgy.
The basis of the “Tridentine” liturgy was the rite of the Roman Curia. This Ritus Curiae Romanae evolved at the turn of the 11th—12th century on the basis of old Italian and Roman traditions. In comparison with the other cathedral rites, it was a somewhat simplified variant of the same common order. The motivation for simplicity was twofold: limiting the increase of the Frankish-Roman liturgy (e.g., indifference toward the Offices of new saints, slowing the growth of trope and sequence repertory); and the separation of priests working in the Curial bureaucracy from the elevated public sung liturgy of cathedrals and parishes.
And thus many rich elements of the Holy Week liturgy, for example, fell victim to the Curial reform.
To sum up: the “Tridentine” liturgy belongs to the family of the Roman liturgy. All its essential features are identical with that liturgy. In other words, it is one of the many variants of the Roman liturgy – the ‘Tridentine” liturgy is Roman liturgy! In this sense, the “Tridentine” liturgy exists not only since the 16th , but since the 8th or 9th, or in some sense since the 4th century. But the Roman liturgy is not identical with the “Tridentine” liturgy: it is more than that. Those who follow the “Tridentine” liturgy, celebrate the Roman liturgy. But the Roman liturgy also lived in other, and in certain respects perhaps more perfect, forms.
Is the confusion of terminology in contemporary discourse the outcome of neglect or lack of knowledge? Instead, I think it is a conscious and malevolent deception.
When the choice is described in terms of the dichotomy: “conciliar liturgy — ‘Tridentine’ liturgy,” an impression is created that the matter concerns the opposition of two liturgical forms which are equally “zeitbedingt” or time-bound. The logic of this mentality is that the “Tridentine” rite is the liturgy of the Renaissance and Baroque periods, which perhaps worked well for the past 300 years, but today the needs of a new age and of modern man must be met with the new Vatican II liturgy. Accordingly, he who favors the “Tridentine” liturgy over the “conciliar” one desires to perpetuate the formalities of bygone times, and thus endangers the renewal of the Church. But if, on the contrary, the “Tridentine” liturgy in its essence is nothing other than the ancient Roman liturgy itself, it cannot be written off as Renaissance or Baroque or “zeitbedingt.” And then, the truth is that the recent innovations overrode not some 300-year-old custom, but in fact broke with the entire tradition of the Roman Church insofar as it is recognizable for us.
Laszlo Dobszay, The Bugnini-Liturgy and the Reform of the Reform (2003)