“The Christian faithful who come together as one in expectation of the Lord’s coming are instructed by the Apostle Paul to sing together Psalms, hymns, and spiritual canticles (cf Col 3:16). Singing is the sign of the heart’s joy (cf. Acts 2:46). Thus St. Augustine says rightly, ‘Singing is for one who loves,’…”
-General Instruction of the Roman Missal (p39)