Originally Posted by chas_m

Okay, crystal clear explanation and you are perfectly right in that case, two libraries would be the best for that purpose.

I took a listen to the soundcloud samples, I get the impression these are designed for club or for people to sing/rap over? If so, I'd say well done -- I like to downtempo "groove salad" vibe on them.

So, how to switch back and forth between libraries? Simple -- launch iTunes holding the option key, you'll be prompted to create a new library or change libraries. The last one selected remains the default until a new one is selected.