One of the things people most frequently notice about churches of Christ is that we sing without the use of mechanical instruments of music - a capella singing is the only music used in our worship.
Simply stated, here is the reason: we are seeking to worship according to the instructions of the New Testament. The New Testament leaves instrumental music out, therefore, we believe it right and safe to leave it out too. If we used the mechanical instrument we would have to do so without New Testament authority.
There are only 8 verses in the New Testament on the subject of music in worship: Here they are:
"And when they had sung a hymn, they went out to the Mount of Olives" (Matthew 26:30)
"...about midnight Paul and Silas were praying and singing hymns to God..." (Acts 16:25)
"Therefore I will praise thee among the Gentiles, and sing to thy name" (Romans 15:9)
"...I will sing with the spirit and I will sing with the mind also" (1 Corinthians 14:15)
"...be filled with the Spirit, addressing one another in psalms and hymns and spiritual songs, singing and making melody to the Lord with all your heart" (Ephesians 5:18, 19)
"Let the word of Christ dwell in you richly, as you teach and admonish one another in al wisdom, and as you sing psalms and hymns and spiritual songs with thankfulness in your hearts to God" (Colossians 3:16)
"I will declare thy name unto my brethren, in the midst of the church I will sing praise unto thee"(Hebrews 2:12)
"Is any one among you suffering? Let him pray. Is any cheerful? Let him sing praise" (James 5:13)
The mechanical instrument of music is conspicuously absent in these passages.
Historically, the first appearance of instrumental music in church worship was not until the sixth century A.D., and there was no general practicing of it until after the eighth century.
Instrumental music was strongly opposed by such religious leaders as John Calvin, John Wesley and Charles Spurgeon because of its absence in the New Testament.