It's 9:30 on a Thursday night and Chinese and foreign jazz fans descend on the JZ Club in Shanghai's former French Concession. Glasses clink and the splashing sound of cymbals ripple through a cabaret setting bathed in soft red light.

Andrew Field, an American historian, says clubs like JZ represent a return to Shanghai's cosmopolitan past.

"You will see Chinese musicians playing with Western musicians or African musicians," says Field, who works at nearby Duke Kunshan University. "Jazz really became the soundtrack of the modern city, not just in Shanghai, but worldwide in the '20s and '30s. It was the musical language of the city. It was about speed."

I'm out on the town this evening with Field and James Farrer, a sociologist at Sophia University in Tokyo. They've written Shanghai Nightscapes: A Nocturnal Biography of a Global City.

Over two decades of research – which included a lot of bar hopping – the pair covered Shanghai night life from its colorful heyday in the 1920s and 1930s, to its resurgence, which began in the 1980s. Today, the city has more than 2,000 bars as well as music and dance clubs, according to Dianping, China's equivalent of Yelp.

After drinks on the club's rooftop terrace, we sit down with Ren Yuqing, who founded JZ. In earlier days, Ren, a bassist, says it wasn't easy to find places to play different genres of music.

"We all played in bars or restaurants, but the problem is you cannot play what you want," says Ren. "If you play a lobby lounge in a five-star hotel, the manager will say: 'You guys too loud, too loud, too loud!'"

Friends introduced Ren to jazz and 11 years ago, he opened JZ, which also has its own music school and riverfront festival. The club attracts an eclectic crowd, which this evening includes a group of female musicians who play traditional Chinese music.

What attracts them to jazz? "Jixing," they answer. That's Mandarin for "improvisation," something Chinese music – and society – aren't generally known for.

We leave JZ and walk a couple of blocks to our next destination, El Coctel, a high-end cocktail bar. Along the way, people are selling hashish, which is common in this part of the city. A Philippine prostitute propositions us. Her Mandarin is so good, I initially confuse her for a Chinese.

Sex, drugs and alcohol were part of the fabric of Shanghai nights in pre-Communist days. Field says during the colonial era, sailors filled raucous bar streets with names like the Trenches and Blood Alley, where establishments sometimes closed up at 8:30 the next morning.

After Mao took control of China in 1949, those nightspots disappeared and notoriously capitalist Shanghai largely went quiet.

Today, the city has far more sophisticated spots like El Coctel, which is laid out like a big, living room. The Spanish bartender, Borja, recommends a South Side, a mix of gin, mint, lime and sugar, which he says was popular with the Chicago mafia during prohibition and costs about $13.

Field says El Coctel isn't a platform for the ostentatious display of wealth, but a place to convey sophistication and taste. The clientele here are no longer brawling foreign sailors, but Chinese professionals, many of them female.

"This is something that if we go back 30 years is unimaginable," says Farrer. At that time, few Chinese women went out drinking at bars. "It was something foreign and therefore it was decadent and if you went there, you were sort of a bad woman."

What is genuinely decadent is the final stop of the night: MYST, one of Shanghai's best-known dance clubs. Field has a long drive home to Kunshan, so he drops us off outside the club.

Inside, MYST is a mix of techno music, strobe lights, couches and tables covered with bottles of expensive champagne. Away from the thumping music, Farrer analyzes the scene.

"Almost the entire dance floor is covered by table seating," he says. "So in a place where people would have danced and mingled and get to know each other is really privatized space. Just like the rest of Shanghai, where everybody wants to own real estate, now young people really want to own real estate at the clubs."

We bump into Teejay, a local university student from Nigeria and a promotor whom the club pays to bring in customers. Teejay, who doesn't want to give his full name because he's not supposed to be working on a student visa, says rich Chinese spend at least $500 for a table and a lot more on drinks.

"They buy 30 bottles of champagne and they only get to drink two," says Teejay. "They just want to show off."

What happens to all the champagne that's purchased, but never consumed?

"The club takes it back," says Teejay. "It's the club's profit."

Farrer says this is a turnaround from the early days of clubbing in Shanghai when there was room to dance and for people from different walks of life to connect. Now, they just sit in groups and stare at their cell phones. Farrer finds it depressing.

"You see people not really communicating with each other," he says. "You see dance clubs where, quite frankly, almost nobody is dancing. It's all about you controlling your space, hanging out with your friends and showing off your money to a very limited number of people."

Farrer says it's also a sign of how stratified China's richest city has become.

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