CATECHISM OF THE CATHOLIC CHURCH
SECOND EDITION

Paragraphs 1154–1157

1154 The liturgy of the Word is an integral part of sacramental celebrations. To nourish the faith of believers, the signs which accompany the Word of God should be emphasized: the book of the Word (a lectionary or a book of the Gospels), its veneration (procession, incense, candles), the place of its proclamation (lectern or ambo), its audible and intelligible reading, the minister's homily which extends its proclamation, and the responses of the assembly (acclamations, meditation psalms, litanies, and profession of faith).
1155 The liturgical word and action are inseparable both insofar as they are signs and instruction and insofar as they accomplish what they signify. When the Holy Spirit awakens faith, he not only gives an understanding of the Word of God, but through the sacraments also makes present the "wonders" of God which it proclaims. The Spirit makes present and communicates the Father's work, fulfilled by the beloved Son.
1156 "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 solemn liturgy." The composition and singing of inspired psalms, often accompanied by musical instruments, were already closely linked to the liturgical celebrations of the Old Covenant. The Church continues and develops this tradition: "Address . . . one another in psalms and hymns and spiritual songs, singing and making melody to the Lord with all your heart." "He who sings prays twice."
1157 Song and music fulfill their function as signs in a manner all the more significant when they are "more closely connected . . . with the liturgical action," according to three principal criteria: beauty expressive of prayer, the unanimous participation of the assembly at the designated moments, and the solemn character of the celebration. In this way they participate in the purpose of the liturgical words and actions: the glory of God and the sanctification of the faithful:

How I wept, deeply moved by your hymns, songs, and the voices that echoed through your Church! What emotion I experienced in them! Those sounds flowed into my ears distilling the truth in my heart. A feeling of devotion surged within me, and tears streamed down my face - tears that did me good.