I just got a used Mac mini and am running Yosemite. I decided I wanted all my music on an external drive (I have about 400 GB). I followed every instruction I can find on the Internet and nothing has worked. When I open iTunes i only see my purchased songs that have been pulled down from the cloud and any song that I have played during testing. I have found on my external drive where the purchased songs are residing and if I move a song there it will not show up in iTunes. It's driving me nuts! What do I do?