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The 11 talented young people, who proved to be receptive and open-minded, surprised him eventually.
"When I'm bringing a language that is very idiosyncratic, generally I try to water that language down. I walked in and the feeling in the room was good-natured and curious and supportive, and so I was able to throw them my best shots, and nobody flinched," he recalls.
"When it was challenging, no one said no and when it was fun, people laughed, and I really felt like I got everything I needed to make it work here, which is pretty unusual."
But, it was no surprise for an ensemble of professional dancers, who cherished the opportunity of working with a renowned choreographer like Petronio more than anything else.
For 25-year-old Josef Perou, By Singing Light provides a stage to learn from established dancers and show off his own techniques. As the newest member of National Dance Company Wales, Perou works hard to perfect his movements.
"I have to focus on the two sections of the dance. The first section is very practical and functional, and then the choir comes in and it changes completely - it's a lot more confrontational in the approach to the movement; you make direct eye contact with the audience. So before the dance, I need to prepare myself for this change in gear," he says.
Other than training and rehearsals, aftercare is an important element for dancers.
"You also have to keep yourself fit and healthy, and get treatment if you need it, to help with an injury," Perou says.
Emerging as a leading name on the international contemporary dance stage, National Dance Company Wales has a very hectic schedule this year.
Apart from touring China, the group is also performing in various parts of the United Kingdom.
Contact the writer at liujinmei@chinadaily.net.cn.