There are some who have assumed that because we find no direct reference to instruments in the New Testament, none were used in worship. But that is not necessarily the case. It is possible they were not used as much because of their association with pagan and idolatrous worship of the Romans and Greeks. But that would be a cultural or associative exclusion rather than one that was prescribed by God's Word for all people, places, and times. The other possibility is that instruments were not used as much during the time of the Roman persecution of Christians because it would have drawn attention to their secret meetings. Christians in hiding would not have wanted to use trumpets and cymbals to draw attention to themselves.
In I Corinthians 14 Paul talks about order and the importance of the church being built up. In the midst of that passage he alludes to instruments. In James 5:13 James says, "Is anyone among you suffering? Let him pray. Is anyone cheerful? Let him sing praise." Twice in I Corinthians 14:15, Romans 15:9 and Ephesians 5:19 the verb for "sing" is psallo. This word for sing, unlike the word ado in some passages, meant "sing to the accompaniment of instruments". In Ephesians 5:19 we are basically challenged to sing "with one's whole being," which draws a parallel to Psalm 150 - "Let everything that has breath praise the Lord!"
Instruments make valuable contributions to congregational singing - leadership, support of melody, color, energy and interpretive meaning to text and message. While all instruments may be "lawful" for use in worship, all may not be "appropriate" according to associations with pagan worship and false worship in our own time as we have also seen in the New Testament. We also must take into account that some good things can be redeemed from mis-use and benefit the work of the Lord. A line between liberty and legalism requires great spiritual wisdom and prayerful humility. Thank God He promises to give wisdom liberally when we ask in faith (James 1:5). May we wisely and with humility use instruments for the glory and exaltation of our Lord God! mjm