Iran's supreme leader, Ayatollah Ali Khamenei, has said that music is not compatible with the values of the Islamic republic, and should not be practised or taught in the country.

In some of the most extreme comments by a senior regime figure since the 1979 revolution, Khamenei said: Although music is halal, promoting and teaching it is not compatible with the highest values of the sacred regime of the Islamic Republic.

Khamenei's comments came in response to a request for a ruling by a 21-year-old follower of his, who was thinking of starting music lessons, but wanted to know if they were acceptable according to Islam, the semi-official Fars news agency reported. It's better that our dear youth spend their valuable time in learning science and essential and useful skills and fill their time with sport and healthy recreations instead of music, he said.

Khamenei has rarely expressed his views on music publicly, but he is believed have played a key role in the crackdown on Iran's music scene following the revolution. When Khamenei was president, he banned western-style music, forcing many stars to go into exile.

Tehran's chief of police, Hossein Sajedi-Nia, has revealed the fate of young Iranians who are attracted to what he calls morally deviant music.

According to Tehran-Emrouz, an Iranian daily newspaper, he said that young Iranian men and women were arrested last week in a score of raids targeting the capital's underground rap scene. The rappers – both male and female – had apparently taken over vacant buildings in order to create what Iran's regime has depicted as degenerative, anti-Islamic music.

Across Iran, illicit house parties with smuggled alcohol, large amounts of cannabis, and booming Western music are the norm. Young Iranians believe it is a risk worth taking: As long as we are careful, one partygoer told me, as long as we know who our neighbours are, we can dance to whatever music we want. She is right. More often than not, the Iranian police have turned a blind eye to what Iranians do in the comfort of their own homes.

The regime can tolerate its youth intoxicated. But what it cannot abide is young Iranians actively subverting its authority. Iranian rap is not a direct emulation of what the regime deems messianic American rap; its lyrics often derive from the pain of living under the corruption and abuse of the Islamic Republic.

The establishment of the Islamic regime marked the exodus of talented Iranian musicians from the country. One famous Iranian rapper, Erfan, now lives in California. His lyrics are not about fast cars and money. And they are certainly not, as the Iranian government has suggested, sexually explicit.

In an explicit attack against the Regime, Erfan also wrote Tasmim (Resolution), after the June 2009 Green Movement protests in Iran. One line in particular echoes recent events: Every day you say our Iran is at fault, you say this but you beat and you kill. It is for lyrics like these that the young musicians have been arrested in Tehran.