Since the celebration of Mass by its nature has a “communitarian” character,45Cf. Second Vatican Ecumenical Council, Constitution on the Sacred Liturgy, Sacrosanctum Concilium, nos. 26-27; Sacred Congregation of Rites, Instruction Eucharisticum mysterium, On the worship of the Eucharist, 25 May 1967, no. 3d: AAS 59 (1967), p. 542. both the dialogues between the priest and the faithful gathered together, and the acclamations are of great significance;46Cf. Second Vatican Ecumenical Council, Constitution on the Sacred Liturgy, Sacrosanctum Concilium, no. 30. in fact, they are not simply outward signs of communal celebration but foster and bring about communion between priest and people.
The acclamations and the responses of the faithful to the priest’s greetings and prayers constitute that level of active participation that the gathered faithful are to contribute in every form of the Mass, so that the action of the entire community may be clearly expressed and fostered.47Cf. Sacred Congregation of Rites, Instruction Musicam sacram, On music in the Liturgy, 5 March 1967, no. 16a: AAS 59 (1967), p. 305.
Other parts, very useful for expressing and fostering the faithful’s active participation, that are assigned to the whole assembly that is called together include especially the Act of Penitence, the Profession of Faith, the Prayer of the Faithful, and the Lord’s Prayer.
Finally, concerning the other formulas: Some constitute an independent rite or act, such as the Gloria, the responsorial Psalm, the Alleluia and verse before the Gospel, the Sanctus, the Memorial Acclamation, and the cantus post communionem (song after communion); Others accompany another rite, such as the chants at the Entrance, at the Offertory, at the fraction (Agnus Dei), and at Communion.