Allegri's Adoremus in Aeternum

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 sacred song united to the words, it forms a necessary or integral part of the solemn liturgy.  (Sacrosanctam Concilium, 112)

  You may not be surprised to know that my tastes in liturgical music tend toward the more traditional.  I'm not disparaging contemporary religious music, in and of itself.  I even like some of it: I have been known to play John Michael Talbot's version of "Table of Plenty", for instance, and I have an abiding fondness for Dana Scallon's "We Are One Body".  Really. These and many others are fine as expressions of religious devotion . . . but are they truly appropriate for the Holy Sacrifice of the Mass? Do they really capture the sacredness of the Miracle of the Holy Eucharist?
      I was once discussing Sacred Polyphony with co-worker, a very talented non-Catholic music teacher, who said of the work of composers such as Palestrina and Allegri: "It's some of the most beautiful music I've ever heard.  I can't believe they got rid of it in the liturgy;  I mean, I guess they had to, but It's hard to believe."  It's understandable that he might believe this; many Catholics do, too.  On the other hand, the Church itself, in the Second Vatican Council's Constitution on the Sacred Liturgy Sacrosanctum Concilium says: 

The Church acknowledges Gregorian chant as specially suited to the Roman liturgy: therefore, other things being equal, it should be given pride of place in liturgical services.

But other kinds of sacred music, especially polyphony, are by no means excluded from liturgical celebrations, so long as they accord with the spirit of the liturgical action, as laid down in Art. 30.

     The word sacred means "set aside", as in set aside for God, and so sacred music should be very special indeed.  I offer as an example the clip below, which employs both Gregorian Chant and Polyphony, Gregorio Allegri's "Adoremus in Aeternum".

Section VI of Sacrosanctum Concilium, dealing with Sacred Music:

VI SACRED MUSIC

112. 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 sacred song united to the words, it forms a necessary or integral part of the solemn liturgy.

Holy Scripture, indeed, has bestowed praise upon sacred song [42], and the same may be said of the fathers of the Church and of the Roman pontiffs who in recent times, led by St. Pius X, have explained more precisely the ministerial function supplied by sacred music in the service of the Lord.

Therefore sacred music is to be considered the more holy in proportion as it is more closely connected with the liturgical action, whether it adds delight to prayer, fosters unity of minds, or confers greater solemnity upon the sacred rites. But the Church approves of all forms of true art having the needed qualities, and admits them into divine worship.

Accordingly, the sacred Council, keeping to the norms and precepts of ecclesiastical tradition and discipline, and having regard to the purpose of sacred music, which is the glory of God and the sanctification of the faithful, decrees as follows.

113. Liturgical worship is given a more noble form when the divine offices are celebrated solemnly in song, with the assistance of sacred ministers and the active participation of the people.

As regards the language to be used, the provisions of Art. 36 are to be observed; for the Mass, Art. 54; for the sacraments, Art. 63; for the divine office. Art. 101.

114. The treasure of sacred music is to be preserved and fostered with great care. Choirs must be diligently promoted, especially in cathedral churches; but bishops and other pastors of souls must be at pains to ensure that, whenever the sacred action is to be celebrated with song, the whole body of the faithful may be able to contribute that active participation which is rightly theirs, as laid down in Art. 28 and 30.

115. Great importance is to be attached to the teaching and practice of music in seminaries, in the novitiates and houses of study of religious of both sexes, and also in other Catholic institutions and schools. To impart this instruction, teachers are to be carefully trained and put in charge of the teaching of sacred music.

It is desirable also to found higher institutes of sacred music whenever this can be done.

Composers and singers, especially boys, must also be given a genuine liturgical training.

116. The Church acknowledges Gregorian chant as specially suited to the Roman liturgy: therefore, other things being equal, it should be given pride of place in liturgical services.

But other kinds of sacred music, especially polyphony, are by no means excluded from liturgical celebrations, so long as they accord with the spirit of the liturgical action, as laid down in Art. 30.

117. The typical edition of the books of Gregorian chant is to be completed; and a more critical edition is to be prepared of those books already published since the restoration by St. Pius X.

It is desirable also that an edition be prepared containing simpler melodies, for use in small churches.

118. Religious singing by the people is to be intelligently fostered so that in devotions and sacred exercises, as also during liturgical services, the voices of the faithful may ring out according to the norms and requirements of the rubrics.

119. In certain parts of the world, especially mission lands, there are peoples who have their own musical traditions, and these play a great part in their religious and social life. For this reason due importance is to be attached to their music, and a suitable place is to be given to it, not only in forming their attitude toward religion, but also in adapting worship to their native genius, as indicated in Art. 39 and 40.

Therefore, when missionaries are being given training in music, every effort should be made to see that they become competent in promoting the traditional music of these peoples, both in schools and in sacred services, as far as may be practicable.

120. In the Latin Church the pipe organ is to be held in high esteem, for it is the traditional musical instrument which adds a wonderful splendor to the Church's ceremonies and powerfully lifts up man's mind to God and to higher things.

But other instruments also may be admitted for use in divine worship, with the knowledge and consent of the competent territorial authority, as laid down in Art. 22, 52, 37, and 40. This may be done, however, only on condition that the instruments are suitable, or can be made suitable, for sacred use, accord with the dignity of the temple, and truly contribute to the edification of the faithful.

121. Composers, filled with the Christian spirit, should feel that their vocation is to cultivate sacred music and increase its store of treasures.

Let them produce compositions which have the qualities proper to genuine sacred music, not confining themselves to works which can be sung only by large choirs, but providing also for the needs of small choirs and for the active participation of the entire assembly of the faithful.

The texts intended to be sung must always be in conformity with Catholic doctrine; indeed they should be drawn chiefly from holy scripture and from liturgical sources.

(from Sancrosanctum Concilium, 4 December 1963)