I was looking at the reference in Amos 6 and did notice "Am 6:5 That chant to the sound of the viol, and invent to themselves instruments of musick, like David".

I also looked at 2 Chronicles 7:6 "And the priests waited on their offices: the Levites also with instruments of musick of the LORD, which David the king had made to praise the LORD, because his mercy endureth for ever, when David praised by their ministry; and the priests sounded trumpets before them, and all Israel stood."

I don't see that David did anything wrong. So, at first glance, they (in Amos 6) were guilty of doing as David did only for evil.

Maybe I missed it. Am I missing the point (honest question)?