Renowned singer-songwriter Liu Huan, who was a judge of The Voice of China, says it's encouraging to see these subway artists follow their dreams. He also points out that street performers are common in Western countries, and many don't do it just to make money but, rather, because they enjoy it.
China's situation is a little different because most such musicians not only aim to entertain others but also hope to break into fame.
In the past, a singer usually would get noticed only after he or she performed on TV or at national galas. But now, people can show off their voices through many other channels, Liu says.
Like Xu, 33-year-old singer Chen Hanrang spends hours singing and playing guitar on the subway. The performance is also a way to audience-test the music of his band, Tong Zi Gu, which he founded in 2009 with four other amateurs.
Inspired by Hong Kong pop-rock band Beyond, Chen gave up a stable job at an instrument store and came to Beijing in 2009 to pursue his dream.
He met his band mates after he used trashcans for percussion during street performances they happened upon.
In January 2012, the band was invited to perform at Beijing TV Station's Spring Festival gala with other grassroots singers and groups, such as Xuri Yanggang.