It would be possible to do this cleverly by using the iPod Note Reader functionality. You wouldn't have to rename anything, you'd just have to put both files on the iPod and then create some clever note files which would let you play them without seeing any real information about them.
This documentation would be what you need to do it:
http://developer.apple.com/hardware/ipod/ipodnotereader.pdfYou would need to create the Preferences file with the line:
<meta name="NotesOnly" content="true">
in it, to prevent the person from exiting the note reader. You'd also need:
<meta name="NowPlaying" content="false">
in there, to keep your song links from displaying the now playing screen.
Then you create some notes to let you play a bunch of different X's, like X1, X2, X3, etc.. Each one of these randomly points at either track A or track B. Then the user can play each and write down which he thinks it is. Afterwards, he can compare and check his results. You could also create links to A and B so he can play those for comparison purposes.
Then all he has to do to get the iPod back to normal would be to connect it to a PC and delete the Preferences file off the iPod.
This would not be particularly difficult to demonstrate, if anybody is interested. Writing a program to generate the notes would be fairly trivial as well.