Reply to Objection 4: As the Philosopher says (Polit. viii, 6), "Teaching should not be accompanied with a flute or any artificial instrument such as the harp or anything else of this kind: but only with such things as make good hearers." For such like musical instruments move the soul to pleasure rather than create a good disposition within it. In the Old Testament instruments of this description were employed, both because the people were more coarse and carnal---so that they needed to be aroused by such instruments as also by earthly promises---and because these material instruments were figures of something else.
Reply to Objection 5: The soul is distracted from that which is sung by a chant that is employed for the purpose of giving pleasure. But if the singer chant for the sake of devotion, he pays more attention to what he says, both because he lingers more thereon, and because, as Augustine remarks (Confess. x, 33), "each affection of our spirit, according to its variety, has its own appropriate measure in the voice, and singing, by some hidden correspondence wherewith it is stirred." The same applies to the hearers, for even if some of them understand not what is sung, yet they understand why it is sung, namely, for God's glory: and this is enough to arouse their devotion.