65 In rites that are not completely liturgical religious hymns of this kind - when, as We have said, they are endowed with the right qualities - can be of great help in the salutary work of attracting the Christian people and enlightening them, in imbuing them with sincere piety and filling them with holy joy. They can produce these effects not only within churches, but outside of them also, especially on the occasion of pious processions and pilgrimages to shrines and at the time of national or international congresses. They can be especially useful, as experience has shown, in the work of instructing boys and girls in Catholic truth, in societies for youth and in meetings of pious associations.
Source: Musicae Sacrae (Vatican.va)