Moving then spanning external iTunes library
I have a number of iTunes libraries, the main one is located on an external drive. How do I make this library local on my laptop and then spanned back to an external drive? Do I first have to copy this external library onto the laptop (its pretty large, would need work to make room for it) and then span it back?
I also have iTunes match: how does this work with a spanned library if the external drive is not connected (and say one downloads that song to the local drive)?
What is the best procedure for merging songs from one library to another (I seem to have songs in one library that are not part of another for various reasons).