I believe the following method still works with the 6th gen nano, I know it does with older generations. If you enable hidden folders on your computer you should be able to go to the iPod in Finder/Explorer and see a hidden folder called Music. The files in here you won't be able to make out unless you play them, because the iPod changes their file names. Once imported into iTunes/Music they should have the proper name and associated info however. From there you can copy it all to the second iPod. Hopefully this works still