(Constitution on the Liturgy, page 2)

Pastors of souls must therefore realize that, when the liturgy is celebrated, something more is required than the mere observation of the laws governing valid and licit celebration. It is their duty also to ensure that the faithful take part fully aware of what they are doing, actively engaged in the rite, and enriched by its effects. (11)

Mother Church earnestly desires that all the faithful should be led to that full, conscious, and active participation in liturgical celebrations which is demanded by the very nature of the liturgy. Such participation by the Christian people is their right and duty by reason of their baptism. They are "a chosen race, a royal priesthood, a holy nation, a people redeemed." (1 Peter 2:9; cf. 2:4-5).

IN THE RESTORATION AND PROMOTION OF THE SACRED LITURGY, THIS FULL AND ACTIVE PARTICIPATION BY ALL THE PEOPLE IS THE AIM TO BE CONSIDERED BEFORE ALL ELSE.  It is the primary and indispensable source from which the faithful are to derive the true Christian spirit.  Therefore, pastors of souls must zealously strive to achieve it, by means of the necessary instruction, in all their pastoral work.

Yet it would be futile to entertain any hopes of realizing this unless the pastors themselves, in the first place, become thoroughly imbued with the spirit and power of the liturgy, unless they undertake to give instruction about it. A prime need, therefore, is that attention be directed, first of all, to the liturgical instruction of the clergy. (14)

. . . With zeal and patience, pastors of souls must promote the liturgical instruction of the faithful, and also their active participation in the liturgy, both internally and externally, taking into account their age and condition, their way of life, and standard of religious culture. By so doing, pastors will be fulfilling one of the chief duties of a faithful dispenser of the mysteries of God. In this matter, they must lead their flock not only in word but also by example. (15)

. . . Liturgical services are not private functions but are celebrations of the Church, which is the "sacrament of unity," namely, the holy people united and ordered under their bishops.

Therefore, liturgical services pertain to the whole body of the Church; they manifest it and have effects upon it. They concern, however, the individual members of the Church in different ways, according to their differing rank, function, and actual participation. (26)

It is to be stressed that whenever rites, according to their specific nature, make provision for communal celebration involving the presence and active participation of the faithful, this way of celebrating them is to be preferred, so far as possible, to a celebration that is individual and quasi-private.

This applies with special force to the celebration of Mass and the administration of the sacraments, even though every Mass has of itself a public and social nature. (27)

In liturgical celebrations, each person, minister or lay person who has a function to carry out should do all (but only) those parts which pertain to his function, by the nature of the rite and the principles of liturgy. (28)

Servers, lectors, commentators, and members of the choir also exercise a genuine liturgical function.  Therefore, they ought to discharge their task with the sincere piety and decorum  demanded by so exalted a ministry and rightly expected of them by God's people.

Consequently, they must all be deeply imbued with the spirit of the liturgy, each in his own measure. They must be trained to carry out their functions in a correct and orderly manner.  (29)

To promote active participation, the people should be encouraged to take part by means of acclamations, responses, psalmody, antiphons, and songs, as well as by actions, gestures, and bodily attitudes.  At the proper times, all should observe a reverent silence. (30)