Hazrat Grand Ayatollah Khamenehie:
Any type of mutrib music which befits carouse gatherings is haram.
Hazrat Grand Ayatollah Fazel Lankarani:
Any type of mutrib music which befits carouse gatherings is haram. In any other instance then there is no problem, and the place from which it is broadcasted does not affect the ruling.
Hazrat Grand Ayatollah Behjat:
If music is mutrib then hearing, buying and selling it is haram.
Hazrat Grand Ayatollah
That which the common culture recognizes as music is haram, and listening, composing, teaching, learning, and selling musical instruments is also haram.
Hazrat Grand Ayatollah Makarim Shirazi:
Any melodies or songs which befit libidinous pleasure and corruption are haram, and anything other than that is halal. This is distinguished by referring to the public common culture.
Hazrat Grand Ayatollah Tabrizi:
Listening to music which befits gatherings of revelry is not permissible. It is also not permissible to make, teach, buy or sell frivolous musical instruments.
Hazrat Grand Ayatollah Sistani:
If music does not befit frivolous gatherings, then it is not haram. Therefore, listening to songs and mutrib music which befits frivolous gatherings is haram.
Distinguishing whether or not a specific music such as rap music is a type of instance or applicability of haram or halal, is the responsibility of each individual. Because, any individual that has even a concise understanding of music can differentiate between music that is mutrib and befits frivolous gatherings and music that is not like that. Therefore, even if revolutionary or war songs are mutrib and befit frivolous gathering then listening to that type of music will also be haram.
Rap music is no acception to this rule, and if it were to fall under the category of mutrib and befitting carouse gatherings then it also would be haram.
Of course the reason why mutrib music that befits frivolous gatherings is haram is another topic. In general it can be said that divine laws are based on divine knowledge and wisdom and the benefits and indecencies of every ruling has been explained and established, and no one other than Allah, The Most High has complete awareness of them. The knowledge which is at man’s disposal is the correlated laws and some of their wisdom and philosophies. In the case of music it can be said that any collection of factors which impede staying on the right path, higher spirituality, a calm and balanced lifestyle and reflection, or that cause nervousness, psychological apprehension, deficiency of the mind, impulsive gratification, artificial stimulation and desire, and cause dissociation with the realities of life are prohibited. Particularly, the side effects and illnesses caused by listening to fast and impulsive music that is associated with frivolous gatherings. Many books and articles have been written on this topic, one titled "The effect of music on the psyche and nerves", which can be referred to and read for more information. Carouse gatherings which incorporate frivolous and mutrib music, have many other negative affects, but here we will not initiate those discussions.