Congregation for Divine Worship and the Discipline of the Sacraments, General Instruction of the Roman Missal (2003).
41. All other things being equal, Gregorian chant holds pride of place because it is proper to the Roman Liturgy. Other types of sacred music, in particular polyphony, are in no way excluded, provided that they correspond to the spirit of the liturgical action and that they foster the participation of all the faithful.*
Since faithful from different countries come together ever more frequently, it is fitting that they know how to sing together at least some parts of the Ordinary of the Mass in Latin, especially the Creed and the Lord’s Prayer, set to the simpler melodies.**
* Cf. Second Vatican Ecumenical Council, Constitution on the Sacred Liturgy, Sacrosanctum Concilium, no. 116; cf. also Sacred Congregation of Rites, Instruction Musicam sacram, On music in the Liturgy, 5 March 1967, no. 30.** Cf. Second Vatican Ecumenical Council, Constitution on the Sacred Liturgy, Sacrosanctum Concilium, no. 54; Sacred Congregation of Rites, Instruction Inter Oecumenici, On the orderly carrying out of the Constitution on the Sacred Liturgy, 26 September 1964, no. 59: AAS 56 (1964), p. 891; Sacred Congregation of Rites, Instruction Musicam sacram, On music in the Liturgy, 5 March 1967, no. 47: AAS 59 (1967), p. 314.