Why is there a difference in fatwas regarding the ruling on music? Is this disagreement acceptable? Will a person who adopts one of these opinions be held accountable? And how do some people deem musical instruments permissible without also deeming permissible what preceded them [in the Prophetic Hadith], namely zina (fornication/adultery), silk, and alcohol?

The disagreement regarding the prohibition of musical instruments is very weak. No permission for any of them is known from any of the Imams, and the opinion of their permissibility is an outlier. Whoever deems musical instruments permissible without a sound interpretation after clarification is exposed to a warning [of punishment]. As for deeming something permissible (istihlal), it may be by believing that it is permissible, or by continuously engaging in it as if it were permissible. The ruling on deeming forbidden things permissible varies depending on the forbidden item. Deeming alcohol and fornication permissible is disbelief, whereas deeming silk and musical instruments permissible may occur from some scholars due to specious arguments and invalid interpretations. These are among the slip-ups for which one hopes Allah will forgive their perpetrator.