“C UT! THAT was dead awful. Deliver with more passion!” roars He Xiaoying at a group of adolescent girls who had been rehearsing a comedy routine. Ms He is the eponymous head of a boarding school in the north-eastern city of Changchun, in China’s rust belt. Her mission is to train young people in the art of errenzhuan, or “two-person turn”, a traditional form of comic song-and-dance that often involves raunchy gags. The children also study subjects that are more academic, but these take a back seat.

There are at least a dozen such schools in the three provinces of the north-east where errenzhuan originated. Ms He’s 80-odd students, most from poor backgrounds, dream of appearing on national television, or, failing that, at a well-known theatre. In a region plagued by unemployment, some people see a promising future in comedy.

Errenzhuan requires arduous training. It involves duets, typically between a man and a woman, that are often delivered in seven- or ten-character rhyming lines. The dance is usually in folk style, as is the performers’ dress (though modern touches are permissible). In the north-east, where errenzhuan has many fans, some proudly call it the world’s hardest form of comedy.

It is certainly among the most notorious in China for its bawdiness. A common routine is called “The 18 Touches”. One variant of this involves a female performer cracking lewd jokes while stroking the genitals of her male counterpart (with his trousers on). In 2004 Zhao Benshan, the godfather of errenzhuan and China’s first billionaire comedian, said erren zhuan without smut was not erren zhuan at all.

President Xi Jinping is no fan of lewd comedy. In 2014, in a speech on the role of the arts, Mr Xi said some artists were spewing out “cultural garbage”. He demanded that creative works serve the Communist Party and not “provoke the ecstasy of the senses”. It may be no coincidence that Mr Zhao has not appeared on national television’s Chinese New Year gala since Mr Xi assumed power in 2012. He had once been a regular (in cleaned-up form) on the hugely popular show. Last year Mr Zhao was booted out of the advisory body to China’s parliament. His flamboyant lifestyle may also have contributed to his fall from grace.

Mr Zhao is now leading a campaign to bowdlerise errenzhuan. In his chain of theatres he puts on only family fare. Dirty jokes and swearing are all but banned. Other venues have followed suit. Television stations only invite the cleanest erren zhuan performers. Ms He, the head teacher, says she does not teach her students any dirty lines or gestures. A Changchun resident says this trend may explain why attendance at errenzhuan theatres is falling.

But head to public parks in the north-east and you will find the art form refreshingly unchanged. Errenzhuan entertainers often make extra money with impromptu, open-air gigs. On a recent afternoon in Changchun’s Labour Park, an animated crowd surrounds an errenzhuan duo. Egged on by the audience, the pair engage in profanity-laced banter and sway their hips suggestively. After the show the crowd disperses, but quickly forms again around another act nearby. It involves a male performer reaching up his female partner’s dress. The woman smiles at him seductively, then slaps his face. The park’s security guards, whose job might be supposed to include putting a stop to such displays, appear happy to watch.