From Lux Occidentalis, by Fr. John Connely
Used by permission.
One of the myths presently circulating about the Rite of St. Gregory the Great is that it is "Tridentine"—i.e., it is no older than the Council of Trent [1545-1563]. This criticism is made by those who know nothing about either this Rite or the Council of Trent or the Missal of Pius V . In fact, all that was done at Trent, liturgically speaking, was to standardize the worship of the West. This was done principally in two ways:
First, the Council (together with Pope Pius V) suppressed all Western Rites that did not have a continuous history of at least two hundred years. This effectively eliminated all but the Ambrosian Rite of Milan, the Mozarabic Rite of Toledo, Spain, and the Gregorian Rite of the City of Rome itself, sometimes therefore called the Roman Rite. [* Simple variations within the Roman Rite, such as existed among the Benedictines, Dominicans, etc., were permitted to remain, but have lapsed since the liturgical reforms of the 1960s.] In the 16th century the Gregorian or Roman Rite already had a continuous documented history of more than 1000 years. It therefore became the standard Rite of most of post-Schism Western Christendom. Session XXII [17 Sept. 1562] of the Council issued a series of definitions on the sacrificial doctrine of the Mass, but no change in the actual text of the Rite.