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 regard to praising Him in the Old Testament is now unacceptable in the New Testament church.
Since instrumental music has the Old Testament precedent of being approved of God ("musical instruments of God" 1 Chronicles 16:42), and there is no evidence that there was a time when this approval ceased, I believe that we have biblical authority for its validity.
We are authorized to use “psalms” in the NT (Ephesians 5:19; Colossians 3:16). 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 means "to twitch, twang or pluck," such as pluck a string of a musical instrument."
Strong's Concordance
psalmos: a striking (of musical strings), a psalm
Original Word: ψαλμός, οῦ, ὁ
Part of Speech: Noun, Masculine
Transliteration: psalmos
Phonetic Spelling: (psal-mos')
Short Definition: a psalm
Definition: a psalm, song of praise, the Hebrew book of Psalms.
HELPS Word-studies
5568 psalmós – a psalm ("Scripture set to music"). Originally, a psalm (5568 /psalmós) was sung and accompanied by a plucked musical instrument (typically a harp), especially the OT Psalms.
[The Psalms of the OT were often sung and were accompanied by sophisticated musical arrangements].
NAS Exhaustive Concordance
Word Origin
from psalló
Definition
a striking (of musical strings), a psalm
NASB Translation
Psalm (1), psalm (1), Psalms (3), psalms (2).
The words "making melody" are used in Ephesians 5:19, but "how" this is done is found in Isaiah 23:16, and it is with a musical instrument:" Take an harp, go about the city, thou harlot that hast been forgotten; make sweet melody, sing many songs, that thou mayest be remembered."
Also, Amos 5:23 speaks of "the melody of thy viols," which is also reference to a musical instrument. So if "the Bible interprets itself," these passages show "how" to make melody – with musical instruments.
*If a particular church wants to leave out musical instruments in their worship, that is their prerogative. But I don't believe that it's right for them to judge other churches who choose to use musical instruments like David did and as the apostle Paul instructed.
