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The music should already be on the computer if you've been syncing it...

Otherwise, you can't move it to the computer unless it's something that you bought from iTunes off of the device.
 
What?
When you plug into iTunes, it asks to update.
Click yes.
Purchase the apps.

Viola.
No music gone, just updated firmware/apps.
Well that didn't work for me and I clicked help and it took me to a site on how to do it then at the end it said if all fails to take it off manual so yea.
 
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