The scene and sounds outside

It's after midnight in Chicago. I was trying to sleep, but the roar of the crowds passing by our front door just made it impossible. So I gave up and leaned out of the window with a video camera. It was something like the 4th of July after the fireworks, a scene that never fails to remind me of our Founder's words, "Where and toward what is humanity moving?"
I also have to admit I wonder where and how those sudden waves of screaming originate. People will be walking happily by and then all of a sudden, the throng erupts in shouting, cheering, whistling, chanting. A group just passed by with drums or buckets, tapping out a rhythm for all to chant with.
See if this works to give you some idea.