Answer:
Singing and music, especially Gregorian chant, are associated with the liturgy. The Gregorian chant, also called cantilena Romana, has been, since its codification, (putatively under Pope St. Gregory the Great, although actually occurring later,) and remains the official music of the Latin Rite Catholic Liturgy, prescribed by Church documents to be given "pride of place" in Her liturgies. This form of music of the Church is contained in the Sacramentary Roman Missal as well as the chant books, e.g. graduale Romanum, antiphonale, liber cantualis. Other Rites within the Catholic Church, (e.g. Maronite, Byzantine, Ambrosian) have their own forms of chant which are proper to their Divine Liturgies. Gregorian chant provides the Latin Church with a musical identity, and like the ancient Liturgical language, provided and still provides Her Liturgies with a unifying element as Her catholicity ("universality',) has become more apparent, via the international travel of recent popes, worldwide media originating in the Vatican, etc. Also associated with the liturgy are sacred images, which proclaim the same message as do the words of Sacred Scripture sung to the sacred melodies of the chant, and which help to awaken and nourish faith.
The 1967 document Musicam sacram, that implemented the Constitution on the Sacred Liturgy after the Second Vatican Council, repeatedly mentions facilitating the full, active participation of the congregation as called for by the Council.[2][3] so that "unity of hearts is more profoundly achieved by the union of voices.[4] Musicam Sacram states: "One cannot find anything more religious and more joyful in sacred celebrations than a whole congregation expressing its faith and devotion in song. Therefore the active participation of the whole people, which is shown in singing, is to be carefully promoted."[5] It calls for fostering this congregational participation through attention to choice of song directors,[6] to choice of songs,[7] and to the nature of the congregation.[8] It mentions the duty to achieve this participation on the part of choirs, choirs directors, pastors, organists, and instrumentalists.[9] To achieve full, active participation of the congregation, great restraint in introducing new hymns has proven most helpful.[10] To this end also, the General Instruction of the Roman Missal recommends use of seasonal responsorial psalms and also keeping to a song that all can sing while processing to Communion, to “express the communicants’ union in spirit by means of the unity of their voices, to show joy of heart, and to highlight more clearly the ‘communitarian’ nature of the procession to receive Communion.”[11]
