I am of the opinion that the whole 13-pin, synthesizer, piezo, stereo, mike-plug issue is far from decided, or at least far from decided well. The 1/4" phone plug is a rather archaic, low-rent way of plugging anything in, but it currently still wins by overwhelming numbers. I wish I knew the answer (there be bucks here, mateys) but I'm not gonna be the one showing up at a jam session with a dual Speak-On cord (and a pocket full of 13-pin adapters) and asking them why their amps are so retarded.