Before the time of Christ, God's children worshiped Him through the observation of laws, feast days, sacrifices, and offerings. Many types and symbols were used. This worship included the use of musical instruments. Their use is mentioned frequently in the Old Testament, and especially in the Psalms. David was a singer who was skilled in their use.
In the gospel era, offerings, sacrifices, types, and symbols have been replaced by Jesus, the Lamb of God. Jesus fulfilled the law. The sacrifices and rituals so important to the Old Testament-era worshipers were abolished, and worship from the heart became the only acceptable worship. "Therefore if any man be in Christ, he is a new creature: old things are passed away, behold, all things are become new" (2 Corinthians 5:17). Salvation is of the heart. God is worshiped and praised from the heart.
There is no evidence in the New Testament that the apostolic Church used musical instruments. There is little mention of them in the New Testament other than as examples for comparison (1 Corinthians 13:1; 14:7), and in Revelation referring to music in heaven (Revelation 14:2; 15:2).
Paul, in his sermon to the Athenians, declared that God is not "worshipped with men's hands, as though he needed any thing, seeing he giveth to all life, and breath, and all things" (Acts 17:25). Vocal singing is repeatedly exemplified and commanded in the New Testament. Jesus sang a hymn with His disciples. "And when they had sung an hymn, they went out into the mount of Olives" (Matthew 26:30, Mark 14:26). "And at midnight Paul and Silas prayed, and sang praises unto God: and the prisoners heard them" (Acts 16:25). James wrote, "Is any merry? let him sing psalms" (James 5:13). Paul instructed Christians to sing psalms, hymns, and spiritual songs (Ephesians 5:19; Colossians 3:16; 1 Corinthians 14:15).
God is concerned that the worshiper's heart and spirit be pure and his will set to do God's will at any cost. Jesus said, "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" (John 4:23).