37 The tunes of these hymns, which are often sung in the language of the people, are memorized with almost no effort or labor. The mind grasps the words and the music. They are frequently repeated and completely understood. Hence even boys and girls, learning these sacred hymns at a tender age, are greatly helped by them to know, appreciate and memorize the truths of the faith. Therefore they also serve as a sort of catechism. These religious hymns bring pure and chaste joy to young people and adults during times of recreation. They give a kind of religious grandeur to their more solemn assemblies and gatherings. They bring pious joy, sweet consolation and spiritual progress to Christian families themselves. Hence these popular religious hymns are of great help to the Catholic apostolate and should be carefully cultivated and promoted.
Source: Musicae Sacrae (Vatican.va)