Contradiction with 1 Chronicles 15:16
Contradicts by suggesting a broader group of Levites were appointed for music, not just those from the family of Kohath.
1 Chronicles 15:16: And David spake to the chief of the Levites to appoint their brethren [to be] the singers with instruments of musick, psalteries and harps and cymbals, sounding, by lifting up the voice with joy.
Contradiction with 1 Samuel 8:7
Indicates that God was their ruler, suggesting a direct rule rather than mediated by human institutions set up like David appointing music leaders.
1 Samuel 8:7: And the LORD said unto Samuel, Hearken unto the voice of the people in all that they say unto thee: for they have not rejected thee, but they have rejected me, that I should not reign over them.
Contradiction with 2 Chronicles 5:12
Mentions that all Levites, not just specific ones, were involved in music which contradicts the specific appointment in 1 Chronicles 6:31.
2 Chronicles 5:12: Also the Levites [which were] the singers, all of them of Asaph, of Heman, of Jeduthun, with their sons and their brethren, [being] arrayed in white linen, having cymbals and psalteries and harps, stood at the east end of the altar, and with them an hundred and twenty priests sounding with trumpets:)
Contradiction with Amos 6:5
Suggests that making music was associated with self-indulgence, contrary to the sacred service context in 1 Chronicles 6:31.
Amos 6:5: That chant to the sound of the viol, [and] invent to themselves instruments of musick, like David; [chant: or, quaver]