My brother was a member of the Church of Christ which is why I know something about their beliefs. They didn’t use musical instruments when singing songs because, as he told me, musical instruments were not mentioned in the first century church. Neither was electricity, but that sure didn’t keep them from having electric lights and air conditioning. Maybe things have changed or that was particular to his church and not assembly wide, I don’t know.

Churches which follow the New Testament don't use instrumental music. As noted it is because of the absence of authorization for their use in the New Testament. However, your analogy fails to make your point. Musical instruments did exist during the first century. The use of musical instruments was authorized under the Old Testament law (Psalm 150 is an example). It is because the Law of Christ specifically mentions singing (Ephesians 5:19; Colossians 3:16) and does not mention insturmental music in worship which makes us sit up and take notice of this change.