A semi-common sight in DC are street musicians, people who stand on street corners or sit just inside the entrances of Metrorail stations and play instruments of one sort or another. Every once in a while you'll see one within spitting distance of an office building, something that has become a bit more rare since 9/11 since physical security has become such a big deal in this country. Most people don't even stop to listen to them because they're too busy doing what they need to do to keep their lives running smoothly, which seems to consist of running …