audio ouput from usb midi keyboard?

Question, I was wondering if you can use a usb MIDI keyboard with the 4000 in the same since as you would with an ordinary MIDI keyboard. From what I'm researching, its MIDI cables or nothing! Just wondering if that is the case or if someone knows how to... Thanks

no i know the usb ports arent for that... i was running from the audio output of the keyboard.. im just going to purchase a real MIDI keyboard and stop trying to make things work.... oh well