What about the biblical letters written to Christians? What do they say about Christian worship? If we want to hear familiar instruments—perhaps just a harp—we may be surprised. In the letters, no such instrument is heard in the divine recording of the church’s worship. The only music heard by human ears is singing that praises God and instructs people.
Christ became a servant… in order that the Gentiles might glorify God for His mercy. As it is written, “Therefore I will praise You among the Gentiles, and sing to Your name.” And again it is said, “Rejoice, O Gentiles, with His people.” And again, “Praise the Lord, all you Gentiles, and let all the peoples extol Him.” (Romans 15:8-11 quoting Psalm 18:49; Deuteronomy 32:43; Psalm 117:1)
I will pray with my spirit, but I will pray with my mind also; I will sing praise with my spirit, but I will sing with my mind also…. When you come together, each one has a hymn, a lesson, a revelation, a tongue, or an interpretation. Let all things be done for building up. (1 Corinthians 14:15, 26)
He [Christ] is not ashamed to call them brothers, saying, “I will tell of Your name to My brothers; in the midst of the congregation I will sing Your praise.” (Hebrews 2:12 quoting Psalm 22:22)
Do not get drunk with wine, for that is debauchery, but be filled with the Spirit, addressing one another in psalms and hymns and spiritual songs, singing and making melody to the Lord with your heart, giving thanks always and for everything to God the Father in the name of our Lord Jesus Christ. (Ephesians 5:18-20)
Let the word of Christ dwell in you richly, teaching and admonishing one another in all wisdom, singing psalms and hymns and spiritual songs, with thankfulness in your hearts to God. (Colossians 3:16)
Is anyone among you suffering? Let him pray. Is anyone cheerful? Let him sing praise. (James 5:13)