Normally it’s only possible to sync media on an iPhone with one computer. If you try to use a second computer you get the warning below that “the iPhone XXX is synced with another iTunes library. Do you want to erase this iPhone and sync with this iTunes library”?

 

However, I’ve found an easy fix for this. In the instructions below I’ll show how to modify any iTunes Library so it can also be synced with your iPhone. You can then either manually manage your iPhone on a second computer, or sync different data on different machines (E.g. Music at home, Contacts/Calendar at work).

Should be useful now for archival purposes.