I. General Norms
5. A liturgical service takes on a nobler aspect when the rites are celebrated with singing, the ministers of each rank take their parts in them, and the congregation actively participates.  This form of celebration gives a more graceful expression to prayer and brings out more distinctly the hierarchical character of the liturgy and the specific make-up of the community. It achieves a closer union of hearts through the union of voices. It raises the mind more readily to heavenly realities through the splendor of the rites. It makes the whole celebration a more striking symbol of the celebration to come in the heavenly Jerusalem.
Pastors are therefore to strive devotedly to achieve this form of celebration. They would do well even to adapt to congregational celebrations without singing the distribution of functions and parts that more properly belongs to sung services. They are to be particularly careful that there are enough necessary, qualified ministers and that the people's active participation is helped.
The truly successful preparation of a liturgical celebration is to be achieved through the cooperation, under the parish priest (pastor) or rector, of all who have a part in the rites themselves and in the pastoral and musical elements of the celebration.
6. To give its true structure to the celebration if the liturgy requires, first, the proper assignment of functions and the kind of execution in which "each one, minister or layperson, who has an office to perform, does all of, but only, those parts which pertain to that office by the nature of the rite and the principles of liturgy."  But an additional requirement is exact fidelity to the meaning and character of each part and of each song. To achieve this end it is above all necessary that those parts which of their nature call for singing are in fact sung and in the style and form demanded by the parts themselves.
7. The amount of singing determines the gradations between the most solemn for of liturgical celebrations, in which all the parts calling for singing are sung, and the most simple form, in which nothing is sung. For the choice of parts to be sung, those should be first that of their nature are more important and particularly those sung by the priest or other ministers and answered by the congregation or sung by the priest and congregation together. Later other parts, for the congregation alone or the choir alone may be added gradually.
8. Whenever a choice of people for a sung liturgical celebration is possible, those with musical talent should obviously be preferred. This is particularly the case with the more solemn liturgical services, those involving more difficult music, or those to be broadcast on radio or television. 
When no such choice is possible and the priest or minister does not have the voice to sing properly, he may recite, audibly and clearly, one or other of the more difficult parts belonging to him. This, however, is not to be done merely to suit the personal preference of the priest or minister.
9. The choice of the style of music for a choir or congregation should be guided by the abilities of those who must do the singing. The Church does not exclude any type of sacred music from liturgical services as long as the music matches the spirit of the service itself and the character of the individual parts  and is not a hindrance to the required active participation of the people. 
10. It is advisable that there be as much suitable variety as possible in the forms of celebration and the degree of participation in proportion to the solemnity of the day and of the assembly, in order that the faithful will more willingly and effectively contribute their own participation.
11. The real solemnity of a liturgical service, it should be kept in mind, depends not on a more ornate musical style or more ceremonial splendor but on a worthy and reverent celebration. This means respect for the integrity of the rites, that is, carrying out each of the parts in keeping with its proper character. More ornate styles of singing and greater ceremonial splendor are obviously sometimes desirable, when they are possible. But it would be in conflict with the genuine solemnity of a liturgical service if such things were to cause any element of the service to be omitted, altered, or performed improperly.
12. The Apostolic See alone has authority to establish, in accord with the norms of tradition and particularly of the Constitution on the Liturgy, those general principles that stand as the foundation for sacred music. The various lawfully-constituted territorial bodies of bishops and the bishops themselves have authority to regulate sacred music within the already defined limits.