Jesus says in John 4:24, "God is spirit and they that worship Him must worship Him in spirit and in truth." Singing has a very definite place in worshipping God "in spirit and in truth". God has commanded each one of us to sing in worship. When people just sit through the worship service and never attempt to sing (unless they can't sing) they are not obeying God. Or when people sit and listen to a choir sing they are not obeying God’s command to sing. There is no Biblical authority for a choir in worship. Congregational a cappella singing is the only kind of music divinely authorized by the Lord for Christian worship.
In Colossians 3:16-17 we read, "Let the word of Christ dwell in you richly in all wisdom, teaching and admonishing one another in psalms and hymns and spiritual songs, singing with grace in your hearts to the Lord. And whatever you do in word or deed, do all in the name of the Lord Jesus." In verse 16 we are commanded to sing. In the very next verse we are told, "whatever you do in word or deed, do all in the name of the Lord Jesus." Everything we do in religion is to be done "in the name of the Lord Jesus, which means by His authority. We can certainly sing by the authority of the Lord. But where would we go in the New Testament for authority for instrumental music in the worship? It just isn’t there.
In 1 Corinthians 14:15 we read, "I will sing with the spirit and I will sing with the understanding also." Not only does an instrument not have a heart, but it also does not have a spirit with which to understand.
God has spoken in the New Testament concerning the kind of music we must use if we expect to worship Him "in spirit and in truth." Singing is the limit of God’s command. God nowhere in the New Testament authorized mechanical instruments of music to be used in worship of the church and to use it is a sin. A lifeless mechanical instrument of music cannot worship.