That God allows and does not forbid, the use of mucial instruments in Worship of Him. There are some who think otherwise.
it's not a matter of whether God allows and does not forbid, or that God does not allow and forbids. It's much more a matter of why a New Testament church OUGHT to sing in acapella.
When King Hezekiah restored temple worship in 2 Chronicles 29 and commanded the burnt offering be offered and the burnt offering was
in process of being offered, verse 27 tells us "the song of the LORD began
also with the trumpets, and with the instruments
ordained by David king of Israe" (note: ordained by a man, David king of Israel".
Of course, we all know that the burnt offering, the passover lamb, the sin offering, almost all types of offering in the Old Testament was representative of Jesus Christ. The New Testament Scriptures also recount to us that the night before He was crucified (offered up as burnt offering) the Savior sang hymns with His apostles.
Now, back to 2 Chronicles 29, and verse 28 tells us that "all the congregation worshipped, and the singers sang, and the trumpeters sounded:
and all this continued until the burnt offering was finished.
Now back in Calvary, our burnt offering is recorded as having exclaimed, Himself, in His own voice "
It is finished.." and Scripture in the same book, chapter and verse, continues..."and He bowed His head, and gave up the ghost." Now back in 2 Chronicles 29, verse 29 says: And when they had made
an end of offering, the king and all that were present with him bowed themselves, and worshipped.
Further, 2 Chronicles verse 30 states, "Moreover Hezekiah the king and the princes commanded the Levites to
sing praise unto the LORD with the WORDS of David, and of Asaph the seer. And they sang praises with
gladness, and they bowed their heads and worshipped.
I suppose since this is a restoration of temple worship, the pattern remains the same.
Instruments ordained by David (a man) while offering was burning, words of the songs written by David (acapella) after the offering has been consumed.
So, the why.
If a church claims to be from, or of, the New Testament church founded by Jesus Christ along the shores of Galilee (and I think very few churches in so called "christendom" will not claim that) well, then, that church OUGHT to be following the pattern set by Scripture (sing with grace and melody with their hearts to the Lord) as well as holding to the doctrines and practices of the original New Testament church.
Otherwise, the claim that they are a New Testament church, or a church descended from the original one, is false.