This is actually one of my favorite images. Each time I see it, it makes me smile. This was taken in Union Square, SF. I was shooting the band Diego's Umbrella. This was a daytime gig, so it was sparsely populated. 

Diego's Umbrella is a very energetic band, and they love to run around the stage and bounce off of each other. In this shot, One of the guitar players has stepped off of the "stage" and onto a small speaker (which would usually be a bass speaker). The speaker was never taken out of it's road case - and you can see that is on wheels. Wheels that do not lock in place. He could have easily had this speaker roll out from under him as he physically put a lot into his performance.

Then there is the fan. She showed up with a group of people in the middle of the performance and was immediately transfixed. She broke away from her group and gravitated toward the stage. For at least 30 minutes, she danced by the stage, and really got down when this event happened. 

The fun part about this photo is that the woman is mentally handicapped and her friends in the group were lured into the music by her enthusiasm..!