not sure if I miss something, but I haven't figured out how to use the tuning knobs :( I tried mouseover, click, click+drag, in vertical and also in horizontal direction, but the tone didn't moved in any direction.
I agree that using the tuning knobs was not very intuitive. I guess that you're supposed to click on the knob, hold it down, and move up or down to tune -- but there was no feedback (except from the sound, which changed slowly.)