Washington, D.C., Metro Station on a cold January morning in 2007. The man with a violin played six Bach pieces for about 45 minutes. During that time approximately two thousand people went through the station, most of them on their way to work. After 3 minutes: a middle aged man noticed there was a musician playing.  He slowed his pace and stopped for a few seconds and then hurried to meet his schedule. 4 minutes later: The violinist received his first dollar; a woman threw the money in the hat and, without stopping, continued to walk. 6 minutes: A young man leaned against the wall to listen to him, then looked at his…