Weiserb is correct. iTunes the software and interface window that you open to determine what songs to sync will still be on your main computer. The actual song files will be on your NAS drive. You iTunes does not care where the actual physical location of the file is (whether directly on the computer, a network drive, or an external hard drive (which is how mine is set up). iTunes is really just acting as a traffic director. You can actually have multiple file folders with music in them and tell iTunes to monitor or "find music" in whatever number of folders you tell it to check. I do this with my server so that I can just move my "Christmas/Holiday" music into and out of my "main server" file versus having iTunes point to different folders. This just works for me as my son has his own music folder(not in full resolution) that I don't want to have to have on my server based system (Slim Devices Duet).
You should still get another external hard drive to back up the music (even though th NAS is supposed to serve this function). But having it all on an external, portable HD allows you to share your entire music collection with your buddies. Just pass around the external HD and they can copy your music and put their music onto your drive for you! This is nice when you get a couple of friends together doing this!
You should still get another external hard drive to back up the music (even though th NAS is supposed to serve this function). But having it all on an external, portable HD allows you to share your entire music collection with your buddies. Just pass around the external HD and they can copy your music and put their music onto your drive for you! This is nice when you get a couple of friends together doing this!