Notes taken from the General Instruction of the Roman Missal copyright © 2002 the International Committee on English in the Liturgy (ICEL) in the English translation. Copyright © 2005 Catholic Bishops’ Conference of England and Wales, in the emendations and editorial arrangement.

46. The rites preceding the Liturgy of the Word, namely the Entrance, Greeting, Penitential Act, Kyrie, Gloria, and Collect, have the character of a beginning, introduction, and preparation. Their purpose is to ensure that the faithful, who come together as one, establish communion and dispose themselves to listen properly to God’s word and to celebrate the Eucharist worthily.
In certain celebrations that are combined with Mass according to the norms of the liturgical books, the Introductory Rites are omitted or performed in a particular way.
The Entrance Song
47. After the people have gathered, the Entrance chant begins as the priest enters with the deacon and ministers. The purpose of this chant is to open the celebration, foster the unity of those who have been gathered, introduce their thoughts to the mystery of the liturgical season or festivity, and accompany the procession of the priest and ministers.
48. The singing at this time is done either alternately by the choir and the people or in a similar way by the cantor and the people, or entirely by the people, or by the choir alone. In the dioceses of England and Wales the options for the Entrance Chant are: (1) the antiphon and psalm from the Graduale Romanum or the Graduale Simplex; or (2) a song from another collection of psalms and antiphons, the text of which has been approved by the Bishops’ Conference of England and Wales.55
If there is no singing at the Entrance, the antiphon in the Missal is re c i t e d either by the faithful, or by some of them, or by a lector; otherwise, it is recited by the priest himself, who may even adapt it as an introductory explanation (cf. no. 31).