In the instance where a conference of bishops deems it needful to permit deeper adaptations of the Mass, the matter is referred to the CDWDS, and a careful set of procedures engaged:
395. Finally, if the participation of the faithful and their spiritual welfare require variations and profounder adaptations in order for the sacred celebration to correspond with the culture and traditions of the different nations, then Conferences of Bishops may propose these to the Apostolic See in accordance with article 40 of the Constitution on the Sacred Liturgy for introduction with the Apostolic See’s consent, especially in the case of nations to whom the Gospel has been more recently proclaimed.[Cf. Sacrosanctum Concilium 37-40] The special norms handed down by means of the Instruction on the Roman Liturgy and Inculturation[Cf. Varietates Legitimae 54, 62-69] should be attentively observed.As regards the procedures in this matter, these should be observed:
Firstly, a detailed preliminary proposal should be set before the Apostolic See, so that, after the necessary faculty has been granted, the detailed working out of the individual points of adaptation may proceed.
Once these proposals have been duly approved by the Apostolic See, experiments should be carried out for specified periods and at specified places. When the period of experimentation is concluded, the Conference of Bishops shall decide, if the case requires, upon pursuing the adaptations and shall submit a mature formulation of the matter to the judgment of the Apostolic See.[Cf. Varietates Legitimae 66-68]
396. However, before proceeding to new adaptations, especially profounder ones, great care shall be taken to promote due instruction of the clergy and the faithful in a wise and orderly manner, so as to take advantage of the faculties already foreseen and to apply fully the pastoral norms in keeping with the spirit of the celebration.
