[Is it obligatory to denounce singing?]

Answer: Singing and its instruments are an evil and reprehensible thing in the view of the scholars of the ummah of Muḥammad (May Allah bless him and his family and grant them peace). A few deviated and ruled it to be lawful and permitted. They fall into two categories:
1. A group who are lax in their religion, such as Ibn ʿAbd Rabbih, author of al-ʿIqd al-Farīd. He ruled it permissible and decided in his book that it is ḥalāl. The proof that he was lax in his religion is what is mentioned in his biography in the introduction to his book: that he was infatuated with drinking wine; and like him are those “scholars” who mix with the rulers.
2. The other group are the Ṣūfīs: they permitted from it what stirs yearning for Allah and softens the heart. This is mentioned in Iḥyā’ ʿUlūm al-Dīn by al-Ghazālī.
Once you know this, then know that the disagreement of these two groups is not considered a valid disagreement and does not undermine the consensus. The first group are lax and negligent, having no concern for the disobedience of Allah, Exalted is He; the fatwā and judgment of a wine-drinker are not accepted at all, likewise the fatwā of those who mix with the rulers – it is not accepted, and it is not permissible to rely upon it. The Messenger (May Allah bless him and his family and grant them peace) warned against “scholars” who associate with rulers: “…so beware of them concerning your religion.”
As for the second group, the Ṣūfīs: their permitting some types of singing – namely that which stirs yearning for Allah and softens the heart – was only due to a benefit they thought they perceived in some kinds of singing, not due to a sharʿī proof. As for the rest of singing, they declared it forbidden. Thus, their disagreement is not considered, because it arises from an opinion they formed, not from a proof; rather, they themselves believe singing to be forbidden, but they have, by their own opinion, excluded one type of it, as we mentioned.
What I have come to know in this era is:
1. That the followers of the Salafī madhhab declare all singing and all instruments of amusement to be forbidden; I have heard this repeatedly in their radio broadcasts.
2. The followers of the Jaʿfarī Imāmī madhhab: I heard this [same prohibition] on Radio Tehran, and the state of Iran has committed itself to banning singing absolutely, neither in radio nor elsewhere, from the establishment of Khomeini’s state until today.
3. The scholars of the Zaydiyyah, in past and present, declare singing and instruments of amusement to be forbidden.
Thereafter, reason itself rules that singing and its instruments are repugnant and ugly, for several considerations that necessitate that:
1. It is the companion and partner of alcohol.
2. It arouses desire and sexual instinct in both sexes and calls to fornication.
3. It is among the practices of the openly immoral, the base, and the people of luxury and heedlessness, not among the practices of people of honour and religion.
4. It distracts from the remembrance of Allah and from the prayer, and occupies the heart with infatuation and passion.
5. Today, colonial powers are striving to corrupt the Muslims, and to corrupt their religion and morals, by various means, among them singing. It is no secret, today, what status singing and singers have of prestige, encouragement, political patronage, huge budgets, and so on. There is no doubt that they have perceived that singing is one of the means that turns the youth away from their religion and corrupts their morals.
Thereafter, numerous narrations have come from the Prophet (May Allah bless him and his family and grant them peace) indicating its prohibition, narrated by the Zaydīs, the Jaʿfarīs, and Ahl al-Sunnah wa’l-Jamāʿah. On that basis, it is obligatory to denounce it and change it.
However, Islam began as something strange and will return to being strange as it began. Thus the generality of Muslim peoples deem it lawful and see no harm in it; indeed, to them it is more lawful than pure cold water. They meet anyone who denounces singing among them with belittlement and mockery; and that is not out of ignorance of the evidences indicating its prohibition. If you tried to make them know those evidences, they would not accept them and would treat them lightly. In such a case, what is obligatory is to avoid them and migrate away from them, and it is not permissible to attend their gatherings of amusement and singing. This is what is appropriate with respect to the generality of people.
As for a man’s own household, his children, his family, those under his authority and those over whom he has power, it is incumbent upon him to decisively cut off singing and remove it entirely.
We have only said all this because of His saying, Exalted is He: “So fear Allah as much as you are able.” [al-Taghābun:16] and “Allah does not burden a soul beyond its capacity.” [al-Baqarah:286]
As for the generality of people: there is no blame upon the believer for leaving off outward denunciation by action – not by his heart or by his keeping away from them – because circumstances today, for the believer, have become like the circumstances that existed in the Abbasid era. For true faith, with what it comprises of righteous deeds and abstaining from evil deeds, has become the thing that is condemned; its possessor is deemed deserving of punishment, expulsion, and stoning.
In such circumstances, what is obligatory upon the believer is to preserve his faith and keep away from the people of disobedience, and it is not permissible for him to expose himself to harm and humiliation.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2