This is a hollow/arch machine I helped make. Tom described to me what these kinds of rigs do, then I went out and got the parts. Initially I had two pulleys in the center, and it didn't work until Troy swapped those out for the one with two tracks. It has since been modified to hold extra weight (the string dangling from the belt holds more weights, which make it harder). It could be a lot more polished, but that's what you get the first time you try to make something. I don't know who invented it, otherwise I'd give credit to that person.
As the video says, you have to help the girls when they first start learning it, mostly because they'll find all sorts of ways to cheat the shapes just to get moving.
Obviously I don't own the rights to this music. Sony does. Sony, please don't sue me.