How can the disagreement regarding the ruling on music be permissible, given the succession of scholars who have declared it unlawful, and is there a permissible disagreement concerning something that is prohibited?

The ruling on music has been clarified in previous fatwas.

As for scholarly consensus (ijma') after a difference of opinion (ikhtilaf), it is divided into four categories as expounded by Al-Mawardi in "Al-Hawi Al-Kabir":

1. A difference of opinion occurring after a consensus in the same era: This difference of opinion prevents the formation of a consensus. 2. A consensus occurring after a difference of opinion in the same era: This consensus removes the preceding difference of opinion. 3. A difference of opinion occurring after a consensus in two different eras (e.g., the consensus of the Companions and the difference of opinion among the Successors): If the difference of opinion is in agreement with the fundamental principles, then the preceding consensus is established, and the subsequent difference of opinion is a discarded novelty. If a difference occurs in additional or omitted attributes, the consensus regarding the original attributes is established, and the difference concerning the new attributes is permissible according to Al-Shafi'i and the majority of jurists. However, the Zahiriyyah maintain the validity of the ruling from the initial consensus. A corollary of this is that, according to Al-Shafi'i and the majority of jurists, the burden of proof rests on the one who denies as well as the one who affirms. 4. A consensus occurring after a difference of opinion in two different eras (e.g., the disagreement among the Companions and the consensus of the Successors on one of the two opinions): The majority of Al-Shafi'i's followers hold that the ruling from the previous disagreement remains valid, and the subsequent consensus is not established, because the passing of the Companions with two opinions is considered a consensus on the permissibility of ijtihad (independent reasoning).

Consensus is one of the textual proofs and it is permissible to transmit it through solitary reports (akhbar al-ahad). If the narrator decisively states their consensus, it is accepted. However, if he says, "I did not know of any difference among them," consensus is not established by his narration unless he is one of the people of ijtihad.