Question:Choirs and solo supporters say that the entire congregation must sing every word simultaneosly. They say “If we can not have choirs and solos, you can not sing in four-part harmony." How can I respond to them?
Given the simple fact that men and women do not sing in the same range defeats the argument that harmony cannot be used in congregational singing. Even while singing in what is called "unison" multiple notes at octave intervals are being sung.
The reason we have harmony is because the human voice doesn't produce a single note. We sing a base note upon which are numerous harmonics. We preceive a blending of harmonys when those harmonics line up. Barber shop singers refer to "ringing the rafters" when multiple harmonics line up because the frequencies reinforce each other and the result is a louder sound. If only pure notes were required by God, then it would be impossible for the human voice to produce.
However, the point is that God stated that the congregation is to sing. He didn't say what musical style must be used. Therefore, as long as singing is done, then it meets the command of God.
"Speaking to one another in psalms and hymns and spiritual songs, singing and making melody in your heart to the Lord" (Ephesians 5:19).
"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" (Colossians 3:16).
When songs are sung in parts, it remains a fact that the congregation still is singing and thus meeting the Lord's command. The use of choirs and solos do not meet this aspect of Christian worship. See "Choirs and Solos."