Sacrosanctum Concilium

Sacrosanctum Concilium, the Constitution on the Sacred Liturgy, is one of the constitutions of the Second Vatican Council. It was approved by the assembled bishops by a vote of 2,147 to 4 and promulgated by Pope Paul VI on 4 December 1963. The main aim was to achieve greater lay participation in the Catholic Church's liturgy. The title is taken from the opening lines of the document and means "this Sacred Council".
Contents.
"The numbers given correspond to section numbers within the text."
Title and purpose.
As is customary with Catholic documents, the name of this constitution, "Sacred Council" in Latin, is taken from the first line ("incipit") of the document:
Participation of the laity.
One of the first issues considered by the council, and the matter that had the most immediate effect on the lives of individual Catholics, was the renewal of the liturgy. The central idea was that there ought to be greater lay participation in the liturgy.
Popes Pius X, Pius XI, and Pius XII consistently asked that the people be taught how to chant the responses at Mass and that they learn the prayers of the Mass in order to participate intelligently. Now the bishops decreed that: "To promote active participation, the people should be encouraged to take part by means of acclamations, responses, psalmody, antiphons, and songs." Composers should "produce compositions which ... [provide] for the active participation of the entire assembly of the faithful."
After centuries when, with the Mass in Latin, Catholic piety centred around popular devotions, the bishops decreed that "Popular devotions ... should be so drawn up that they harmonize with the liturgical seasons, accord with the sacred liturgy, are in some fashion derived from it, and lead the people to it, since, in fact, the liturgy by its very nature far surpasses any of them."
On 24 August 2017 Pope Francis emphasized that "the reform of the liturgy is irreversible" and called for continued efforts to implement the reforms, repeating what Pope Paul VI had said one year before he died: "The time has come, now, to definitely leave aside the disruptive ferments, equally pernicious in one sense or the other, and to implement fully, according to its right inspiring criteria, the reform approved by us in application of the decisions of the council."
Consilium.
The council fathers established guidelines to govern the renewal of the liturgy, which included, allowed, and encouraged greater use of the vernacular (native language) in addition to Latin, particularly for the biblical readings and other prayers. Implementation of the council's directives on the liturgy was to be carried out under the authority of Pope Paul VI by a special papal commission, later incorporated in the Congregation for Divine Worship and the Discipline of the Sacraments, and, in the areas entrusted to them, by national conferences of bishops, which, if they had a shared language, were expected to collaborate in producing a common translation.