Q: I just got a used fourth-generation iPod touch and there was already pre-loaded music on it. However, when I select the Transfer Purchases option in iTunes it wont transfer any of the music. How can I get the music from the iPod onto my computer?
A: The Transfer Purchases feature in iTunes is only designed for music that was purchased from the iTunes Store from an iTunes Store account that you have access to.
When you choose the Transfer Purchases option, iTunes goes through the connected iPod or iOS device and searches for any content that was purchased from the iTunes Store using an iTunes account that is authorized on your computer. Purchases made with any other iTunes Store account, or content from other sources (CDs, downloads from other music sites, etc) will not be transferred.
If the content on the iPod touch was purchased by a friend or family member, you will need to get their Apple ID and password so you can authorize your computer for that particular account before attempting to transfer purchases. You can do this by going to the Store menu in iTunes and choosing Authorize Computer. A dialog box will appear asking you to enter an Apple ID and password. Note that you can have more than one iTunes Store account authorized on a single computer, and authorizing a second account does not clear any prior authorizations.
Even in this case, however, iTunes will only transfer content that was purchased from the iTunes Store. Since most users also have content acquired from numerous other sources, you will likely need to look at a third-party application to copy any other content that you wish to retrieve from your iPod touch. Our guide to Copying Content from your iPod to your Computer can provide some useful information on how to recover non-purchased content along with some of the tools available to help you do so.