…The Second Vatican Council says that chant is a necessary or integral part of the solemn liturgy; it gives a nobler form to the celebration of the liturgy; and above all, it is specially suited to the Roman Rite and deserves the foremost place within it. When performed in an edifying manner, chant in and of itself “accords with the spirit of the liturgical action,” which cannot be assumed for any other type of music.
Full transcription here.
Traduzione in italiano qui.