The cyclists in front are powering all of the equipment. You’ve just got to check out the rig. The wheels spin the rotor of a generator that feeds into a small battery with just enough juice to keep things going for a few seconds. A meter shows the power level. If it drops below green, lights out. This actually happened shortly after I stopped filming and everyone was treated to an unexpected drum solo. While I was pedaling, I found a direct correlation with the power level and the bass instruments. Kick drums and bass lines really draw a lot of power!
You can still catch the rest of the fest when it rides down to Potrero Hill (16th and Irwin) around 6pm.