Second Vatican Council
Constitution on the Sacred Liturgy
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, and to which the Christian people, “a chosen race, a royal priesthood, a holy nation, a redeemed people” (1 Pet. 2:9, 4-5) have a right and obligation by reason of their baptism.
The musical tradition of the universal Church is a treasure of inestimable value, greater even than that of any other art. The main reason for this pre-eminence is that, as a combination of sacred music and words, it forms a necessary or integral part of the solemn liturgy.
So have the Fathers of the Church and the Roman pontiffs who in more recent times, led by St. Pius X, have explained more precisely the ministerial functions exercised by sacred music in the service of the Lord.
The Church recognizes Gregorian chant as being specially suited to the Roman liturgy. Therefore, other things being equal, it should be given pride of place in liturgical services.