For me, the skeuomorph of a knob is very much not a knob, because it cannot be operated solely by touch.

The knob on the MXR phaser directly connects my fingers and my ears. Once I have to use my visual cortex, it's a book.

And the skeuomorph knob is a terrible skeuomorph because it replaces rotary motion with linear motion...and that linear motion moves the cursor away from the point of interaction and the point of interaction strongly suggests a point graphically because it is a circle.

I guess I will keep going...if the sweet spot on the MxR is 1200, then why not make the pedal a musical preset and get rid of the knob altogether? OK...everyone isn't into the Unix philosophy and phasers have rhythm. But still there is a question whose main answer is marketing.

You can have to many knobs, but also too few. Minimalist UIs are great if you want a particular cool sound that you like, but they get in the way if you want to go beyond that.

A meditation on the merits of minimalist UI.