It’s a hidden interface mapping for sure—you have to know about it before it makes any sense. It might help if a “ghost slider” appeared when you first press o

It’s a hidden interface mapping for sure—you have to know about it before it makes any sense. It might help if a “ghost slider” appeared when you first press on it, but that could also clutter things up. As I said in a reply below, I think the touch interface on flat glass is a stepping stone to VR synths where the skeuomorphism is more natural: grab the knob and spin it, just like hardware!