Q: I have a friend’s iPod with music on it already. She wants some of my music but wants to keep hers. Is there any way possible to add my music without deleting hers.
A: By default, an iPod can only be automatically synchronized with a single iTunes library, and any attempts to automatically synchronize it with a second library will result in all of the existing content being replaced on the iPod with the content from the new library.
However, iTunes also offers you the option to manage the content on your iPod manually, rather than using automatic synchronization. To set the iPod up to do this, simply connect the iPod to your computer, select it in the iTunes source list on the left-hand side, and choose “Manually manage my music and videos” from the “Summary” screen:
Once you apply this setting (by clicking the “Apply” button), iTunes will no longer sync any music or video content to your iPod automatically. Instead, you will need to drag and drop content onto your iPod from your iTunes library in order to add it to your iPod.
However, this setting will travel with the iPod itself, so it will remain in manual mode regardless of which computer you physically connect it to. You can then drag and drop music onto your iPod from any iTunes library that you happen to connect it to.
Note that should you ever return to automatic synchronization, however (by disabling the “Manual” setting above), any content you added to your iPod from another iTunes library that has not been copied into your own iTunes library will be deleted from your iPod. In automatic synchronization mode, the content of your iPod is always a mirror of what is in your iTunes library—no more and no less—so tracks that are not in your local iTunes library are removed from your iPod in automatic synchronization mode
One other thing to note about manual management of the iPod: In manual mode, ratings, play counts, and last played times are not transferred back to your iTunes library, so this data will only be maintained on your iPod. Whether or not this is a serious issue will depend on how you use this information in your iTunes library.