Syncing iPhone 5

Hi Guys,

I have a problem that i'm struggling to find an answer to. I have an iPhone 5 64gb and want to sync my entire music library to it, 30gb.

My library is stored on an external drive, and when I try and sync, it will only sync the local songs that are stored on my macbook pro, and not the stuff from my external drive. I have changed the iTunes file path to the external drive and set this to manage the volume, however it still won't sync.

Any ideas??