I thought this was interesting. Video in the link.
A onetime child prodigy, at 39 Joshua Bell has arrived as an internationally acclaimed virtuoso. Three days before he appeared at the Metro station, Bell had filled the house at Boston's stately Symphony Hall, where merely pretty good seats went for $100. Two weeks later, at the Music Center at Strathmore, in North Bethesda, he would play to a standing-room-only audience so respectful of his artistry that they stifled their coughs until the silence between movements. But on that Friday in January, Joshua Bell was just another mendicant, competing for the attention of busy people on their way to work...
In the three-quarters of an hour that Joshua Bell played, seven people stopped what they were doing to hang around and take in the performance, at least for a minute. Twenty-seven gave money, most of them on the run -- for a total of $32 and change. That leaves the 1,070 people who hurried by, oblivious, many only three feet away, few even turning to look.
...there was never a crowd, not even for a second.
http://www.washingtonpost.com/wp-dyn/content/article/2007/04/04/AR2007040401721.html