They do teach that you are not saved UNTIL you are water baptized. I at one time had attended a church of Christ several years ago when I was a teenager. They had a 5 step plan of salvation that went like this: 1. Hear 2. Believe 3. Repent 4. Confess 5. Be baptized then you are finally saved "after" baptism.
Musical instruments, if used with care, can enhance the singing of praise to the Lord.
That was seen by the Christian church that split from the church of Christ. Musical instruments were obviously considered a help to praise in the Old Testament. It seems strange to say that something God thought was a blessing in the Old Testament and is now an evil in the New Testament church.
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 anyone to judge and condemn others who choose to use musical instruments like David did and as the apostle Paul instructed.