I just got a new MacBookAir for my home. It will primarily be used at home with some occasional use out of the house. I would like to use the iTunes server on my Synology NAS to store a downloaded copy of my iTunes libray for use a time. My understanding is that I can do this by pointing iTunes to the iTunes server directory on my NAS. Here's the issue, I believe that when I am out of the house, it will search for that library and not find it. Will iTunes know to automatically revert to iTunes Match streaming if it can't find the library?
It will not be able to automatically switch. What you'll have to do is create a new iTunes library that is used for streaming only. To do this, open iTunes while holding the Option key. Then selected "Create new library" and name it something different, I used "iTunes Streaming". Then, simply turn on iTunes Match and you'll see all your playlists populate. Once you do this, you'll be able to stream all your music directly from Apple. When you're back home, open iTunes again while holding the Option key and select your original library.