Not fully automatic, but this is the only way I know of doing similar
Create a playlist called Phone Offline (or other name of your choosing)
On the phone, change this playlist settings to be always be available offline
anything you now add to this playlist on the PC will auto download on the phone when you open the music app
for downloading everything you add on your phone automatically on your pc is even easier, open up settings on the PC and there is an option to automatically download songs added on other devices, turn this on and then just add to your collection from the phone, pc will then download them
01-28-2015 11:32 AM