In this text, St. Augustine invites us to sing a “new canticle” to the Lord, a praise that springs from a heart renewed by divine grace. This canticle is not simply words well intoned, but a sincere and joyful expression that goes beyond language, reflecting the greatness of an ineffable God. For St. Augustine, true song is jubilation, a sound that expresses what words cannot. Thus, he encourages us to live in such a way that our very life becomes a praise of God, full of authentic love and joy.
From the commentaries of St. Augustine on the psalms
(Psalm 32, sermon 1, 7-8: CCL 38, 253-254)
Give thanks to the Lord with the zither, play the ten-stringed harp in his honor; sing to him a new song. Put off the old, for you are invited to the new song. New man, new Testament, new song. The new canticle does not respond to the old man. It can only be learned by new men, renewed from their old condition by the work of grace and already belonging to the new Testament, which is the kingdom of heaven. 
All our love sighs for him and sings the new canticle. But it is our life, more than our voice, that must sing the new song. Sing to him a new song, sing to him with mastery. Everyone wonders how he will sing to God. Sing to him, but sing well. He does not admit a song that offends his ears. Sing well, brethren. If you are asked to sing to please someone knowledgeable in music, you will not dare to sing to him without due musical preparation, for fear of displeasing him, since he, as an expert in the matter, will discover defects that would go unnoticed by anyone else. 
Who, then, will lend himself to sing masterfully for God, who knows how to judge the singer, who knows how to listen with critical ears? When will you be able to lend yourself to sing with such art and mastery that you will in no way displease such perfect ears? But behold, he himself suggests to you the way you should sing to him: do not worry about the words, as if they were capable of expressing what delights God. Sing joyfully. This is the song that pleases God, the song that is sung with joy. What does it mean to sing with joy? To realize that we cannot express in words what the heart feels. 
Indeed, those who sing, whether in the harvest, in the grape harvest or in some other intensive work, begin to sing with words that express their joy, but then the joy that invades them is so great that, not being able to express it in words, they do without them and end up in a simple sound of jubilation. The jubilation is a sound that indicates the inability to express what the heart feels. And this way of singing is the most appropriate when it is about the ineffable God. For, if it is ineffable, it cannot be translated into words. And, if you cannot translate it into words and, on the other hand, it is not permissible for you to be silent, the only thing you can do is to sing with joy. In this way, the heart rejoices without words and the immensity of joy is not limited by words. Sing to him with skill and joy.