Sorry, don't have a Mustang to reference, but from what the Fender site says, it seems that FUSE is for editing patches in the Mustang series - there's no indication that's it's for recording audio tracks. If you have a recent Mac, you should already have Garageband included.
Recording over pre-recorded tracks may present a different set of problems. You might have to fly them out to yet another device, so you can mix the pre-recorded material with your own playing.
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