1st, David was not instructing about Levitical worship.
2nd, still answer me: what instruction can the NT Church take from David's instruction to use instruments to worship God in the assembly?
That at one time, David organize the duties of those offering praise to God, which is recorded in II Chronicles 29:25-28 (notice verse 26 "And the Levites stood with the instruments of David, and the priests with the trumpets."), which included assigning duties to those playing various instruments.
so how do we use that to justify playing these various instruments in NT worship when unlike the time of David, only "sing" is commanded... and not one single recording of the NT church ever carrying out any of these forms of worship David did? If we worship the way we want to, even if it like David used to do it, it is called "will worship"
Colossians 2:23 (KJV)
23 Which things have indeed a shew of wisdom in will worship, and humility, and neglecting of the body; not in any honour to the satisfying of the flesh.