Reply to Question regarding plugging in an external source to the MC3000

So the MC3000 can plug in an external source like an ipod into it's controller correct? I've watched and read some reviews regarding the controller and I remember somebody mentioning that you can also plug in a second controller into the MC and using the knob as a sort of crossfader. Has anybody done this or can vouch if that's true? If so, how did it go?