How can I run a partially referenced iTunes library? I have a large number of MP4 videos (non-iTunes purchases) in my iTunes library, which is growing daily. Due to the space it's taking up, I plan to unload these files to an external HDD. Home Sharing is the main reason why I use iTunes for my movie library to begin with (including streaming to my Apple TV, not just only iOS devices connected to my local network).

Here is my dilemma: I cannot, to my knowledge, run a partially referenced iTunes library- where Music is automatically copied to the iTunes Media folder, but Videos are not (but rather referenced on the external hard drive). 

I know I can uncheck "Automatically Copy to iTunes" within iTunes' preferences and drag Music into the "Automatically add to iTunes" folder, but I'm hoping a simpler solution exists, either within iTunes or using third party software. Thank you in advance.

By the way, I'm running OSX Mavericks 10.9.3 and iTunes 11.2.1
Have you look into Tune Span?  http://tunespan.com/