But the hour cometh, and now is, when the true worshippers shall worship the Father in spirit and in truth: for the Father seeketh such to worship him. God is a Spirit: and they that worship him must worship him in spirit and in truth. —John 4:23-24
Musical instruments were used in the Old Testament when service to God was based on ritual and ceremony after the flesh. Worship in the New Testament dispensation is to be in spirit and God instructs His people to sing not to play. A cappella singing is the biblical pattern and practice for God’s church.