From Ven. Pope Pius XII's Encyclical Mediator Dei
In the 63rd Anniversary of the Encyclical
4. You are of course familiar with the fact, Venerable Brethren, that a remarkably widespread revival of scholarly interest in the sacred liturgy took place towards the end of the last century and has continued through the early years of this one. The movement owed its rise to commendable private initiative and more particularly to the zealous and persistent labor of several monasteries within the distinguished Order of Saint Benedict. Thus there developed in this field among many European nations, and in lands beyond the seas as well, a rivalry as welcome as it was productive of results. Indeed, the salutary fruits of this rivalry among the scholars were plain for all to see, both in the sphere of the sacred sciences, where the liturgical rites of the Western and Eastern Church were made the object of extensive research and profound study, and in the spiritual life of considerable numbers of individual Christians.
5. The majestic ceremonies of the sacrifice of the altar became better known, understood and appreciated. With more widespread and more frequent reception of the sacraments, with the beauty of the liturgical prayers more fully savored, the worship of the Eucharist came to be regarded for what it really is: the fountain-head of genuine Christian devotion. Bolder relief was given likewise to the fact that all the faithful make up a single and very compact body with Christ for its Head, and that the Christian community is in duty bound to participate in the liturgical rites according to their station.
6. You are surely well aware that this Apostolic See has always made careful provision for the schooling of the people committed to its charge in the correct spirit and practice of the liturgy; and that it has been no less careful to insist that the sacred rites should be performed with due external dignity. In this connection We ourselves, in the course of our traditional address to the Lenten preachers of this gracious city of Rome in 1943, urged them warmly to exhort their respective hearers to more faithful participation in the eucharistic sacrifice. Only a short while previously, with the design of rendering the prayers of the liturgy more correctly understood and their truth and unction more easy to perceive, We arranged to have the Book of Psalms, which forms such an important part of these prayers in the Catholic Church, translated again into Latin from their original text.
7. But while We derive no little satisfaction from the wholesome results of the movement just described, duty obliges Us to give serious attention to this "revival" as it is advocated in some quarters, and to take proper steps to preserve it at the outset from excess or outright perversion.