Thanks!

All of it it is improvised, all be it some pieces more than others. I often have frameworks that I work off of, but i never play the same thing twice kinda thing.

For example this particular piece, I'm just grooving on a base rhythm (in the feet) and improvising the hell outta the hands.

Also, depending on the tempo of the exercise, the time signatures etc. You need to be pretty malleable with ur music. The instructor can start a specific exercise super slow while the class learns it and then when they speed it up, the initial music doesn't always work & thus I'll have to come up with something else on the fly again.