Help! How do I get music from another computer onto my itunes?

An iPod can be synced with only one iTunes account at a time. once you switched to a new iTunes account or a new computer. You have to authorize your iPod to it at first, then you can upload music and video from the new iTunes to your iPod. But this way will overwrite the originial files on iPod with the new iTunes. You may try this iPod transfer, it can help you copy files from iPod to computer for backup, you can also use it as an iTunes alternative to upload music and video. It will not erase your original iPod files. It's safe and works pretty well for me. http://www.mac-dvd.com/ipod-to-mac-transfer.html Hope it helps. Contact me if you have any other question.

To Apple, "sync" means "make the iPod the same as the computer". You'll have to find 3rd party software to copy the songs from the iPod to the computer, then tell iTunes to make a library of them.