copyThing (formerly iPod.iTunes) does real add-synchronization, even in two directions if desired. copyThing evaluates the source for songs, podcasts, videos and/or playlists that are not in the target and only adds these seamlessly, avoiding duplicates, saving your time. Unlike iTunes' "auto update/sync" function copyThing generally does not delete content in the target. copyThing can also transfer song dependend data like "My Rating", "Last Played", "Play Count", and album artwork.
What's new in this version:
- Tested with iTunes 12.4.2