|Greetings from the Critique Club.
I like this idea for the challenge. My thought on the subject is…it doesn’t necessarily convey the idea of actually “paying” the piper. Maybe for this, a “tip jar” in front of him or maybe him looking at the camera, holding his hand out would help convey “paying” a bit better. Then again maybe I'm just being one of those "rule mongers" :). Of course either of these ideas would entail you interrupting his playing and possibly the whole event, so I suppose they aren’t viable options. I think you did well with what you had to work with.
Your exposure looks very good, considering the sky looks pretty overcast, unfortunately this results in fairly flat lighting (as was mentioned below). About the only thing that I can think of that could help in this situation would be a polarizing filter or an off camera flash illuminating him a bit from the left.
As far as composition goes, I like that you included the microphone stand in the shot. I have to say that the camera angle (height) is rather ordinary and doesn’t help give the subject an “interesting” look. Getting a bit lower (possibly just below eye level) might help make this shot more dynamic and the subject more interesting.
I feel I should mention the background. The background is almost an image in itself, and although that isn’t a bad thing, the subject is the piper. To my eye, the pier, sand and buildings detract from the shot. Not only do they add more for us to look at, they visually intersect his head. A different take on this shot may have been to shoot the piper from the same angle, but from the other side, with the water/sky as a backdrop. This could help keep him as the focus of the image as well as making him stand out even more than he does here.
I hope this helps,