iTunes enhances Apple’s media software in a number of ways. It is used mostly for managing audio and video content for your PC or Mac. If you sync your iPod with iTunes, all of the music on the iPod will be replaced with the music that is available on the computer that you’re using. This is especially problematic if you want to use multiple computers to sync your iPod.
If you wish to stop this from happening, this FAQ will help.
Avoid Deleting Music When Syncing iPod
When you connect your iPod to the computer, click the iPod icon, then tick Manually manage music.
Next, create a playlist, adding all of the songs that you want to put onto your iPod. Then, under the iPod icon, click Music. Under the Autofill from section, select the playlist that you have created and click Autofill.
The new songs will be added without deleting those that are already on the iPod.
