If singing is tempered to a gravity befitting the presence of God and angels, it both gives dignity and grace to sacred actions, and has a very powerful tendency to stir up the mind to true zeal and ardor in prayer. We must, however, carefully beware, lest our ears be more intent on the music than our minds on the spiritual meaning of the words. Augustine confesses (Confession, Book 10, chapter 33) that the fear of this danger sometimes made him wish for the introduction of a practice observed by Athanasius, who ordered the reader to use only a gentle inflection of the voice, more akin to recitation than singing. But on again considering how many advantages were derived from singing,  he inclined to the other side.If this moderation is used, there cannot be a doubt that the practice is most sacred and salutary. On the other hand, songs composed merely to tickle and delight the ear are unbecoming the majesty of the Church, and cannot but be most displeasing to God.
- From The Institutues of the Christian Religion, p.551.