I said I'd share the tool I wrote, and so share I shall.
It's command-line based - generally it's "java -jar MIDIFlipper.jar <input> [<output>] [-preserveOctaves]". I've put in two .bat files that will run on any single file you drag into it, however, in the interest of speeding things up. (Sorry for the lack of GUI; maybe someday...)
"-preserveOctaves" does its best to reposition the center of each track as close as possible to the original track's center, so bass lines remain bass lines, instead of getting all squeaky. It's not perfect, though, particularly if a single track goes both very high and very low, so some manual adjustment would likely be recommended.
If you omit an output file, it'll put it in the same folder as the input, with "(flipped)" appended before the ".mid" (or "(flipped, octaves kept)" if relevant).
Also note that this doesn't work on MUS files, just MIDI ones. If you try to flip something that doesn't have a proper MIDI header, it'll abort.
Also, this program also flips pitch bends and RPN fine/coarse tuning, something I've noticed some MIDI flippers lack.
Oh, and here you go, Gez. Dunno if that'd actually work on the Xbox itself, but there you are, all the same.
EDIT: Updated link to point to Dropbox instead of Fileden. That last link for Gez is just gone, though.
Last edited by Shadow Hog on 10-22-13 at 23:43