As Tim and I were walking through Tiananmen Squarein July 2002...

...I decided to get out my guitar and play "Olympia, WA" by Rancid. We knew there was a chance that I'd get arrested, so Tim started taking pictures. That's the Imperial Palace in the background. You can barely make out the picture of Mao.

It didn't take long for a substantial crowd to gather. The Chinese are very enthusiastic, and there are a lot of people in Tiananmen Square all day. That's the Great Museum of the People's Excellent Revolution in the Background.

But before I finished my second song they sent a police officer backed up by a very large Paddy Wagon to talk to me, and I really wanted to get through the last chorus of "New Sensations" by Lou Reed. In the background you can see Mao's tomb and the Great Obelisk for the Great Soldiers Who Died in the Patriotic Wars of the People. Mao lays in state just like Lenin. The only difference is that most people in China seem to really think their dead revolutionary was a great guy; the come in from the provinces and line up for hours to see him.

Although the Paddy Wagon was an implied threat, the police officer didn't arrest me or ask me to move on. He just started asking me questions. "What is your name?" "How long you live in China?" "May I see your passport?" (Which I'd left at the hotel) "What hotel do you live in?" "What other cities do you visit in China?" "What other countries do you visit in Asia?" They found a cop who spoke pretty good English. 

Although he didn't say anything about my guitar playing, I got tired of answer questions so eventually I said, "Would you like me to stop playing my guitar and go?"
"You would leave? Yes, thank you."
I resisted the reflex to say "Thank you" back and said, "You're welcome."
The whole thing was over in about 10 minutes. And as this was pretty much the way we expected it to go, it was basically a contrived happening. Something to do before we went out for Chinese food.
The police don't stop you from playing elsewhere in China. I played on the main shopping street in Beijing, on the Great Wall, on the Waterfront in Shanghai, and a lot of other places, big crowds gathered and nobody hassled me. I think the Chinese police are just a little sensitive about anything that draws a crowd in Tiananmen Square. And don't think that I took a big risk by provoking the police like this. The Chinese government is really supersensitive about their reputation in the west. They don't want to do anything to give them a bad reputation with foreigners or anything that will discourage tourists from coming. So, I was really completely safe as long as I didn't do anything out of bonds like say, "Mao was bad."
While we're on the subject, why do you suppose they call it a "Paddy Wagon?" I think it's because the Paddy Wagon came into use when police forces in many U.S. cities were dominated by the Irish. However, they also call it a Paddy Wagon in England, and I'm quite sure there has never been a time at which the Irish dominated the English police force.