Athanasius insists that the psalms be sung, not said:
But we must not omit to explain the reason why words of this kind should be not merely said, but rendered with melody and song; for there are actually some simple folk among us who, though they believe the words to be inspired, yet think the reason for singing them is just to make them more pleasing to the ear!
This is by no means so; Holy Scripture is not designed to tickle the aesthetic palate, and it is rather for the soul's own profit that the Psalms are sung. This is so chiefly for two reasons. In the first place, it is fitting that the sacred writings should praise God in poetry as well as prose, because the freer, less restricted form of verse, in which the Psalms, together with the Canticles and Odes, are cast, ensures that by them men should express their love to God with all the strength and power they possess. And, secondly, the reason lies in the unifying effect which chanting the Psalms has upon the singer.
For to sing the Psalms demands such concentration of a man's whole being on them that, in doing it, his usual disharmony of mind and corresponding bodily confusion is resolved, just as the notes of several flutes are brought by harmony to one effect; and he is thus no longer to be found thinking good and doing evil, as Pilate did when, though saying I find no crime in Him, he yet allowed the Jews to have their way; nor desiring evil though unable to achieve it, as did the elders in their sin against Susanna - or, for that matter, as does any man who abstains from one sin and yet desires another every bit as bad. And it is in order that the melody may thus express our inner spiritual harmony, just as the words voice our thoughts, that the Lord Himself has ordained that the Psalms be sung and recited to a chant.
Moreover, to do this beautifully is the heart's desire and joy, as it is written, Is any among you happy? Let him sing! And if there is in the words anything harsh, irregular or rough, the tune will smoothe it out, as in our own souls also sadness is lightened as we chant, Why then art thou so heavy, O my soul, why dost thou trouble me? and failure is acknowledged as one sings, My feet were almost gone, and fear is braced by hope in singing, The Lord is my helper, I will not fear what man can do to me.
Well, then, they who do not read the Scriptures in this way, that is to say, who do not chant the divine Songs intelligently but simply please themselves, most surely are to blame, for praise is not befitting in a sinner's mouth. But those who do sing as I have indicated, so that the melody of the words springs naturally from the rhythm of the soul and her own union with the Spirit, they sing with the tongue and with the understanding also, and greatly benefit not themselves alone but also those who want to listen to them. So was it with the blessed David when he played to Saul: he pleased God and, at the same time, he drove from Saul his madness and his anger and gave back peace to his distracted spirit. In like manner, the priests by their singing contributed towards the calming of the people's spirits and helped to unite them with those who lead the heavenly choir.
When, therefore, the Psalms are chanted, it is not from any mere desire for sweet music but as the outward expression of the inward harmony obtaining in the soul, because such harmonious recitation is in itself the index of a peaceful and well-ordered heart. To praise God tunefully upon an instrument, such as well-tuned cymbals, cithara, or ten-stringed psaltery, is, as we know, an outward token that the members of the body and the thoughts of the heart are, like the instruments themselves, in proper order and control, all of them together living and moving by the Spirit's cry and breath.
And similarly, as it is written that By the Spirit a man lives and mortifies his bodily actions, so he who sings well puts his soul in tune, correcting by degrees its faulty rhythm so that at last, being truly natural and integrated, it has fear of nothing, but in peaceful freedom from all vain imaginings may apply itself with greater longing to the good things to come. For a soul rightly ordered by chanting the sacred words forgets its own afflictions and contemplates with joy the things of Christ alone.