The moment the metal singer Shui Shu spread his arms, Buddhist prayer beads in hand and incense wafting from the stage, his band unleashed a wall of sound on the crowd.

The rapt audience of about 200, many wearing masks, swayed gingerly. By the end of his set, most masks were off.

By the time the night's third band took the stage, the hall was a mosh pit, arms flailing and legs kicking with energy built up during six months of coronavirus shutdowns that kept the lights off in Beijing's underground music venues.

Brazilian metal fan Daniel da Silva Anana, who had packed in among the moshing fans, said he was more worried about slipping on a floor wet with spilled drinks than the coronavirus.

"Finally, the no-metal-concerts spell is broken!"

Live venues in Beijing were recently allowed to reopen at 50 percent capacity, as life in China increasingly returns to normal.

Shui Shu's band Bliss-Illusion is part of the country's small but buoyant heavy metal scene, where bands mix genre standards with Chinese elements.

"In our work, 'black metal' is the form while Buddhism is the content," Shui Shu said about his spiritually inspired music that has been released by French label Anesthetize Productions.

Black metal is a sub-genre that creates a dark, moody atmosphere layering heavily distorted guitars and high-pitched vocals.

"We do not exaggerate pain, we praise happiness," he said in his basement rehearsal space a few days before the show at Omi Space, which on the band's Facebook page he called the "first date after the world stopped".

COVID-19 restrictions had put a halt to rehearsals and performances in a Beijing underground music scene that had been under pressure in recent years, including from local authorities who sometimes shut down events, club managers and promoters said.

Shunzi, lead singer of folk-metal band Dream Spirit, whose members perform in traditional Chinese hanfu garments, used the downtime to write songs, including one about the workers who built two emergency hospitals in Wuhan, the city where the coronavirus was first detected.

"The disease has made me contemplate a lot," he said.

"It also changed my relationship with the guitar player. We have been friends since school years but always quarrelling recently. In the pandemic, we communicated a lot and mended our friendship.”