Study this :
Colossians 3:16 (KJV) Let the word of Christ dwell in you richly in all wisdom; teaching and admonishing one another in psalms and hymns and spiritual songs, singing with grace in your hearts to the Lord.
Especially to the fact it is told for "all" to teach and admonish "one another" with psalms and hymns and spiritual songs, what ever these "psalms and hymns and spiritual songs" are, are to be done to "one another" meaning the command is for "all" so if it is say a guitar, then all MUST learn the guitar so as to play it to "one another" to obey the command...
Now that would be amusing...
What is better is as SoulWeaver said, leave the instruments out, use the voice, actual voice if you have it, internal voice like the one you can use with prayer if your mute, and sing to one another and the Lord, bring a twitch to the heart with the beautiful sound box God made, not man.