General Instruction of the Roman Missal (Third Typical Edition) 2002, International Committee on English in the Liturgy.
393. Bearing in mind the important place which singing has in celebration, as a necessary and integral part of the Liturgy, it is the place of the Conferences of Bishops to approve appropriate melodies, especially for the texts of the Order of Mass, for the people's responses and acclamations, and for the special rites that occur in the course of the liturgical year.
Likewise they may judge which musical forms, melodies, and musical instruments may be admitted into divine worship, in that they are truly apt for sacred use or can be rendered apt.
Musicam Sacram: Instruction On Music In The Liturgy, Sacred Congregation of Rites, 5 March 1967
57. New melodies to be used by the priests and ministers must be approved by the competent territorial authority.
60. The new melodies for the vernacular texts certainly need to undergo a period of experimentation in order that they may attain a sufficient maturity and perfection. However, anything done in churches, even if only for experimental purposes, which is unbecoming to the holiness of the place, the dignity of the Liturgy and the devotion of the faithful, must be avoided.