43 This chant, because of the close adaptation of the melody to the sacred text, is not only most intimately conformed to the words, but also in a way interprets their force and efficacy and brings delight to the minds of the hearers. It does this by the use of musical modes that are simple and plain, but which are still composed with such sublime and holy art that they move everyone to sincere admiration and constitute an almost inexhaustible source from which musicians and composers draw new melodies.
Source: Musicae Sacrae (Vatican.va)