"The metro concert allows more space for free play and it reminds me of when I was 18 years old, we used to play where everybody shops with the keyboard set up and guitar case open. People put in a dollar or two when they passed by," he says.

Young classical pianist Ping Youzhi, who described herself as the type who is easily influenced by the surrounding environment, enjoyed playing for her new audience at the metro station. She played melodies such as Turkish March and For Elise.

"Usually you would dress up in formal dress code for classical concerts. You would not be late or walk out. But, it's a completely different experience to play in metro stations - some of the audience only stay for one piece and there are even some who stay only for a couple of seconds," she says.

Ping says she used to get angry with spectators who cough and make noise as "the most wonderful moment becomes interrupted for no reason and as a performer, you would get frustrated in such circumstances".

"But I never feel that way during metro concerts because the purpose is to educate the audience and let more people know about classical music," she says.

According to Feng Hao, spokesman for Shanghai Shentong Metro Group Co, operator of Shanghai Metro, more than 20 metro concerts have been held in People's Square station on Sunday afternoons since the program started more than four months ago.

Shanghai Symphony Orchestra offered excellent artists, referred to as "cultural volunteers", to roll out the concerts in January. In April, Shanghai Chinese Orchestra, which performs folk music, joined in, says Feng, adding the program won't be one-off event.

"We want it to be sustainable," he says.

Metro concerts attract not only music fans, curious passengers and nearby residents, but also those who arrive an hour early all the way from the other end of the city for their favorite artist. Cao Xinggui, 71, is one of them.

Cao, who used to play the traditional Chinese instrument pipa, a four-stringed Chinese lute, says he traveled a long way to hear Duan Ai'ai, the famous Chinese erhu player on April 21.

The retired worker was sent by his district's community folk orchestra to "learn from the expert".

"They (the rest of the community folk orchestra) will come next weekend," says Cao, adding the format of free concerts in metro stations makes it possible for ordinary people like him to meet professional musicians.

"I cannot afford the price of formal concerts and it's not convenient for us in our 70s to go to the ticket office, get the ticket and then go for the concert," he says. "The good thing about this free concert is that they don't do a sloppy job just because it's free. On the contrary, they take it seriously and do a good job."

In Shanghai, the metro station isn't the only public venue to hold such concerts. Audiences can bring blankets and picnic baskets to the relatively relaxed part of the city's Chenshan Botanical Garden to listen to performances. They can sit or lie on the lawn while listening to classical music and admiring the sunset.

At this year's Chenshan Botanical Garden concert, held on May 19, Prague Symphony Orchestra was one of the performers.

China Maritime Museum also announced its weekly Saturday concerts starting from May.

Wu Xinyi from Shanghai Shentong Metro Group Co, who's also in charge of metro concerts, however, expresses his concerns about coping with overcrowding in public concert venues such as metro stations.

"That's why we keep a close eye on passenger flow and control," says Wu, adding his team is sticking to a few principles such as never inviting celebrities (too many commuters will stop for them) and never bringing in a full symphony orchestra to the metro station.

"Safety concerns are also the reason why we're only having the concert in People's Square station - the venue is big enough."

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