The Recovering Choir Director

Paragraphs 4-6 of Mediator Dei recall the grassroots origins of the Liturgical Movement that took root in the late 19th century and continued throughout the 20th century, right through the publishing of this encyclical. These paragraphs serve to emphasize the good fruits that resulted in the actions of the Liturgical Movement. (My emphases in boldface).

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. [Cf. Apostolic Letter (Motu Proprio) In cotidianis precibus, March 24, 1945]

It is interesting to note that in his 1945 motu proprio In cotidianis precibus referenced above, Pope Pius authorized a re-translation of the Psalms into Latin from their original text, presumably for use in the Divine Office; however, according to one cached source that exists online, he did not impose its use on the Latin rite, but proposed it as an option.