Since Christ never authorized mechanical instruments of music in the New Testament to be used in worship of the church, we might ask, when did man "take it upon himself" to start using them in trying to worship God? It is a historical fact according to early church history, no mechanical instruments of music were ever used in church worship until about the year 670 A.D. At this time the church at Rome introduced an organ which produced such disturbances that it was removed. It was not until about 775 A.D. that it was introduced again, but this time it was kept, even with many people objecting. For many years many churches did not accept the instrument.
Even in the 13th century Thomas Aquinas, a noted Catholic scholar, wrote against its use. This showed that even by the 13th century the instrument had not gained full acceptance. Men wanted to have it their way with no regard to what God had specified. This was a departure from the faith and practice of what God has authorized. Why was the use of mechanical instruments of music totally unknown in the worship of the church for the first six hundred years after the New Testament was written? The word "A Capella" means singing without instrumental accompaniment. It actually means, "as done in the chapel." For the first 600 years of the church "as done in the chapel" meant singing in worship of the church without instrumental accompaniment. This is the way the early church worshipped. Why shouldn’t we also worship this way?
Singing in worship to God is for the purpose of honoring God and teaching one another. Singing is what pleases God. Singing without the instrument of music shows our respect of God and what He says in His word when He specifies our heart as the instrument where the melody is to be made. If we love and respect God we will do everything He says and in the way He says to do it. We will not change, substitute, or add to what He says. We must only sing if we want to worship God "in spirit and in truth."