I just got a new mac and I plugged my phone in to sync my music but not all of my songs went onto my mac. I just got new music on my mac and I want to put it on my phone but it won't let me without clearing the library in my phone to replace it with the one on my mac, which is missing most of the songs from my phone because they won't sync.
MacBook Pro with Retina display, iOS 8.4