Ps 150:4

“The timbrel represents the death of fleshly desire because of honesty itself. Dancing is the agreement of reasonable spirits all saying the same thing and in which there are no divisions. The stringed instruments suggest the unison of the voices of moral excellence and the unity of the organ which is the church of God resting on reflective and active minds.”

“"Praise Him in the timbrel and choir" [Psalm 150:4]. The "timbrel" praises God when the flesh is now changed, so that there is in it no weakness of earthly corruption. For the timbrel is made of leather dried and strengthened. The "choir" praises God when society made peaceful praises Him. "Praise Him on the strings and organ." Both psaltery and harp, which have been mentioned above, have strings. But "organ" is a general name for all instruments of music, although usage has now obtained that those are specially called organ which are inflated with bellows: but I do not think that this kind is meant here. For since organ is a Greek word, applied generally, as I have said, to all musical instruments, this instrument, to which bellows are applied, is called by the Greeks by another name: but it being called organ is rather a Latin and conversational usage. When then he says, "on the strings and organ," he seems to me to have intended to signify some instrument which has strings. For it is not psalteries and harps only that have strings: but, because in the psaltery, and harp, on account of the sound from things below and things above, somewhat has been found which can be understood after this distinction, he has suggested to us to seek some other meaning in the strings themselves: for they too are flesh, but flesh now set free from corruption. And to those, it may be, he added the organ, to signify that they sound not each separately, but sound together in most harmonious diversity, just as they are arranged in a musical instrument. For even then the saints of God will have their differences, accordant, not discordant, that is, agreeing, not disagreeing, just as sweetest harmony arises from sounds differing indeed, but not opposed to one another.”

“Let us praise on timbrel and with dance, when we, firmly set upon a restored way of life, adorn the timbrel of our body with the models of best behavior. Let us praise him on stringed instruments and on the organ as we play the fresh strings that are on our harp, let us also, as with the narrow needs of modesty make melodious sounds to God, cleansing ourselves from all the blight of sin.”