(All citations are from the KJV.)
In Colossians 3:16, we are told, "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." The word "psalms" in this verse is Strong's Greek word G5568, ψαλμός.
Strong's definition for G5568: "a set piece of music, that is, a sacred ode (accompanied with the voice, harp or other instrument; a 'psalm' ); collectively the book of the Psalms."
"a. a striking, twanging
b. of a striking the chords of a musical instrument
c. of a pious song, a psalm."
These psalms were to be accompanied by instruments. Thus, the words of the Apostle Paul teach us that musical instruments are acceptable.
Jesus, himself, did not specifically discuss whether musical instruments should or should not be included in our worship. Consequently, Christians should be extremely cautious about making restrictions when none can be found in the word of God. Let each man stand in the liberty in which Christ has made us free. (Galatians 5:1)
1 Praise ye the LORD. Praise God in his sanctuary: praise him in the firmament of his power.
2 Praise him for his mighty acts: praise him according to his excellent greatness.
3 Praise him with the sound of the trumpet: praise him with the psaltery and harp.
4 Praise him with the timbrel and dance: praise him with stringed instruments and organs.
5 Praise him upon the loud cymbals: praise him upon the high sounding cymbals.
6 Let everything that hath breath praise the LORD. Praise ye the LORD.