Several years ago, Peng Ziyun was at the Shanghai Conservatory of Music, studying music and technology. She learned about sound engineering and wanted to build something of her own. But she didn't know how, and she didn't have anyone to teach her. An Internet search led her to Xinchejian, China's first formal "hackerspace," a community-run workshop where ordinary people tinker with everything from art projects to robots.

Ms. Peng, now 23, wanted to make a tree that could talk. With the encouragement of others at...