How do I lighten the keys?

Hey, thank you very much for the app, it's such a golden piece.

In SeeMusic's youtube videos, are those using a LED visualizer mounted on the keyboard or is it all done by the software? I couldn't find a way to have more control over the lighted area, feels like it lightens in a radius circle on which I don't have control. I was thinking if there's any method to set it more like a rectangle-like lighter instead so that it falls on the key. (using version 4 if that matters)

Thanks!