General Instruction of the Roman Missal #15 “Finally, in the manner the liturgical norms of the Council of Trent have certainly been completed and perfected in many respects by those of the Second Vatican Council, which has brought to realization the efforts of the last four hundred years to bring the faithful closer to the sacred Liturgy especially in recent times, and above all the zeal for the Liturgy promoted by St. Pius X and his successors.”
The GIRM holds that the liturgical reforms of Vatican II were actually a completion and perfection of Trent not a discontinuity. Why? I will leave that for you to find out. The reforms of Trent were missing some of the picture that Vatican II was able to fill.
Defending Vatican II 