i read my manual and it wasnt mentioned
not the white cord its on the bottom outside, near whammy
It's an effects pedal port. It tells you that in the instruction booklet that came with the guitar (ie in the big box, not the one in the game case) and then goes onto say that its not yet in use on the next page. Various sites have also shown the wiring inside the controller to have PEDAL printed on the circuit board which goes to the slot (if further proof were needed). Hope this helps.