6 The voice of the pipe of horn, what is it? The horn rises above the flesh: in rising above the flesh it needs must be solid so as to last, and able to speak. And whence this? Because it has surpassed the flesh. He who wishes to be a horn trumpet, let him overcome the flesh. What means this, let him overcome the flesh? Let him surpass the desires, let him conquer the lusts of the flesh. Hear the horn trumpets....What means this, “Set your affection on things above”?
It means, Rise above the flesh, think not of carnal things. They were not yet horn trumpets, to whom he now spoke thus: “I could not speak unto you, brethren, as unto spiritual, but as unto carnal, even as unto babes in Christ. I have fed you with milk, and not with meat; for hitherto you were not able to bear it: neither yet now are you able. For you are yet carnal.” They were not therefore horn trumpets, because they had not risen above the flesh. Horn both adheres to the flesh, and rises above the flesh; and although it springs from the flesh, yet it surpasses it.
If therefore you are spiritual, when before you were carnal; as yet you are treading the earth in the flesh, but in spirit you are rising into heaven; for though we walk in the flesh, we do not war after the flesh....Brethren, do not reproach brethren whom the mercy of God has not yet converted; know that as long as you do this, you savour of the flesh. That is not a trumpet which pleases the ears of God: the trumpet of boastfulness makes the war fruitless. Let the horn trumpet raise your courage against the devil; let not the fleshly trumpet raise your pride against your brother. “Make a joyful noise in the sight of the Lord the King.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)