Good question, MetalHeadMike touched on the majority of what the contour knob does. It definitely is powerful and makes a very noticable difference in the upper mid. It is almost like a high mid shelf and very slight added beef to the notes. If you "dime" the contour knob on 10, it actually takes the contour knob freq OUT of the circuit, so VERY cool and I find IF you dimed contour it makes it very fast tracking to the extreme. I personally like having contour between 5 - 7 with lead boost on.