In the New Testament, we have been commanded to sing (Eph. 5:19, Colossians 3:16). It is a specific command. There is no implication in this command about mechanical instruments. In every example we have of Christians praising God within the New Testament, it is by singing.
And I heard a voice from heaven, as the voice of many waters, and as the voice of a great thunder: and I heard the voice of harpers harping with their harps: And they sung as it were a new song before the throne, and before the four beasts, and the elders: and no man could learn that song but the hundred and forty and four thousand, which were redeemed from the earth. (Revelation 14:2-3 KJV)
And when he had taken the book, the four beasts and four and twenty elders fell down before the Lamb, having every one of them harps, and golden vials full of odours, which are the prayers of saints. And they sung a new song, saying, Thou art worthy to take the book, and to open the seals thereof: for thou wast slain, and hast redeemed us to God by thy blood out of every kindred, and tongue, and people, and nation; (Revelation 5:8-9 KJV)
So, I'm still left wondering how the new covenant had the effect of rendering musical instruments unacceptable.
I ask this because it seems you believe the entire Old Testament Word of God has been replaced by the New Testament. I am not aware of anything in Scripture to support that view. What I do find is that the old covenant has been superceded by the new covenant. It's not the same, not even close.