Even in the perfect worship of heaven they use harps to aid their praise to God - And I heard a voice from heaven, like the voice of many waters, and like the voice of loud thunder. And I heard the sound of harpists playing their harps. They sang as it were a new song before the throne, before the four living creatures, and the elders; and no one could learn that song except the hundred and forty-four thousand who were redeemed from the earth (Revelation 14:2-3).
In the Old Testament, we read in 2 Chronicles 5:11-14 - And it came to pass when the priests came out of the Most Holy Place (for all the priests who were present had sanctified themselves, without keeping to their divisions), and the Levites who were the singers, all those of Asaph and Heman and Jeduthun, with their sons and their brethren, stood at the east end of the altar, clothed in white linen, having cymbals, stringed instruments and harps, and with them one hundred and twenty priests sounding with trumpets-- indeed it came to pass, when the trumpeters and singers were as one, to make one sound to be heard in praising and thanking the Lord, and when they lifted up their voice with the trumpets and cymbals and instruments of music, and praised the Lord, saying: "For He is good, For His mercy endures forever.."
Ephesians 5:19 says "..speaking to one another with psalms, hymns and spiritual songs.." and correspondingly Colossians 3:16 says to, "..admonish one another with psalms, hymns and spiritual songs." The word "psalm" in the Greek dictionary, definition (#5568): "A set piece of music, i.e. a sacred ode (accompanied with the voice, harp, or other instrument)." The root word of psalm is "psallo" which means to means "to twitch, twang or pluck," such as pluck a string of a musical instrument.
If the church of Christ (or any other church) wants to leave out musical instruments in their worship, that is their prerogative. But I don't believe that it's right for them to judge and condemn everyone else who chooses to use musical instruments like David did, as the angels in heaven do and as the apostle Paul instructed.