What goes on when the sun goes down in a small east central town?

The stores are closed, Main Street is dimly lit, and there is no traffic. A few restaurants and gas stations are open, but no one is walking around town and it is getting late. The moon is starting to shine across the river that flows through town.

Its moonbeams are shining into the windows of the library that sits on a little hill near the back of town. But there is something very different about this moon; the beams are bright and strong. They are reflecting off the river into the library windows and glistening with colors and some sounds! What can that be?