f those interested in liturgical matters have heard it once, they have heard it a thousand times: the ancient form of the Roman Mass shouldn’t be referred to as “Tridentine.” Neither the Council of Trent nor Pope St. Pius V created a new liturgy.
St. Pius V’s missal was largely that used during St. Gregory the Great’s pontificate a millennium earlier. Most additions made since the time of St. Gregory were themselves centuries old. The core of St. Gregory’s missal went back to the earliest centuries of the Church. St. Pius V positively commanded dioceses and religious orders which had unique liturgical rites of at least two hundred years old to maintain their own liturgies.Tridentine and Proud – Crisis Magazine