How to use GarageBand knob controls.

For a long time I had trouble trying to use GarageBand knob controls. It was trial and error and I could never figure out exactly what to do. Looking it up yielded nothing. Then by chance I noticed, while watching an instructional video on something else, the cursor was simply being moved up and down on a knob and the knob moved higher or lower (or left or right if panning). Eureka! How could it be that simple? Agreed?