Introductory Rites of Mass
From the General Instruction of the Roman Missal
46. The rites that precede the Liturgy of the Word, namely, the Entrance, the Greeting, the Penitential Act, the Kyrie, the Gloria in excelsis (Glory to God in the highest) and Collect, have the character of a beginning, an introduction, and a preparation. Their purpose is to ensure that the faithful, who come together as one, establish communion and dispose themselves properly to listen to the Word of God and to celebrate the Eucharist worthily.
47. When the people are gathered, and as the Priest enters with the Deacon and ministers, the Entrance Chant begins. Its purpose is to open the celebration, foster the unity of those who have been gathered, introduce their thoughts to the mystery of the liturgical time or festivity, and accompany the procession of the Priest and ministers.
Reverence to the Altar and Greeting of the Assembled People
49. When they have arrived at the sanctuary, the Priest, the Deacon, and the ministers reverence the altar with a profound bow. Moreover, as an expression of veneration, the Priest and Deacon then kiss the altar itself; the Priest, if appropriate, also incenses the cross and the altar.
50. When the Entrance Chant is concluded, the Priest stands at the chair and, together with the whole gathering, signs himself with the Sign of the Cross. Then by means of the Greeting he signifies the presence of the Lord to the assembled community. By this greeting and the people’s response, the mystery of the Church gathered together is made manifest.
The Penitential Act
51. After this, the Priest calls upon the whole community to take part in the Penitential Act, which, after a brief pause for silence, it does by means of a formula of general confession. The rite concludes with the Priest’s absolution, which, however, lacks the efficacy of the Sacrament of Penance.
The Kyrie, Eleison
52. After the Penitential Act, the Kyrie, eleison (Lord, have mercy), is always begun, unless it has already been part of the Penitential Act. Since it is a chant by which the faithful acclaim the Lord and implore his mercy, it is usually executed by everyone, that is to say, with the people and the choir or cantor taking part in it.
The Gloria in Excelsis
53. The Gloria in excelsis (Glory to God in the highest) is a most ancient and venerable hymn by which the Church, gathered in the Holy Spirit, glorifies and entreats God the Father and the Lamb. The text of this hymn may not be replaced by any other.
54. Next the Priest calls upon the people to pray and everybody, together with the Priest, observes a brief silence so that they may become aware of being in God’s presence and may call to mind their intentions. Then the Priest pronounces the prayer usually called the “Collect” and through which the character of the celebration finds expression. By an ancient tradition of the Church, the Collect prayer is usually addressed to God the Father, through Christ, in the Holy Spirit, and is concluded with a Trinitarian ending.