In China, Cui Jian is not only the country’s biggest rock star, but also one of the most popular critical voices. Banned from performing at large venues in the 1990s because of his veiled critique of the Tiananmen crackdown, he has stayed in the spotlight as director and musician. The 52-year-old rocker performed to an adoring -- but small -- crowd at the Clockenflap music festival in Hong Kong after a six-year hiatus.