Personally, I have this image of their final performance involving this huge crowd, with everyone being divided into small groups, with those without a group being assigned one. Every time the special cord is used, there's a 50% chance one groups collars will go off, split between all at once or one at a time, the time between activations being determined by the size of the group.

Of course, unlike the club, there's no safe areas, and the band is wearing their own collars. If they're selected, no matter what, Silver will be given just enough time to strike the cord one last time. If she manages it, every collar in the crowd will go off simultaneously with Silvers own. If she doesn't, every remaining group has a 50% chance of activating with Silvers.

If Fountain reaches the end alive, and there's no remaining fan groups left, they get to live. If there's only one fan group left, that group gets to decide if they pop or not. If there's more then one left, Fountains collars, along with every remaining groups except one will go off, with that remaining group receiving everything Fountain left behind.

Or maybe everyone who goes to the final performance is guaranteed to die anyway, with Fountain dying at the end with everyone still left. I prefer to leave that hope of surviving though myself.