I recently found this in a trusted review comment. I’m sure I’d lose it so here it is repeated here so I don’t!
iTunes: Requiremnet for me was to have as single place for all music and ideally to share a single library so that you can use either computer to add songs and sync iPods. Solution was to move all music into the “Family Library -> Family Music” folder on the mapped drive and then on the main computer account change the default library source in iTunes within advanced preferences to this network location and check “Copy files to iTunes Music folder when adding to library”. Restart iTunes holding down shift key – select “create new library” and create it again in the same network location. Once this is done and you have enabled sharing in iTunes simply open iTunes on all user accounts on all computers whilst holding shift and “change library location” to the network folder and again in advanced prefs change the library source. Currently any changes I make in any user account in iTunes (playlists song adds etc) are reflected for all iTunes accounts.