Adam,

Serial Cable has nothing to do with recording. Its just like a midi cable.

Instrument files are what calkwalk uses to allow you to choose patch names from within cakewalk, instead of just choosing them by hand on the actual keyboard.

You can take advantage of any of the sounds in the keyboard from the Multi mode, by just changing the bank from which you are choosing sounds. it doesn't have to stay on GM-A or GM-B.