How do I play ONLY internal hard drive content on iTunes?

I have the majority of my iTunes content on an external drive. I'm fine with the way it's set up, and whenever I want to play that content, I plug in my external drive and can play whatever I want.

Most questions I've seen here relate to HOW to set up content on an external drive. I already have done that and have no problems.

My question should hopefully be simple: Is there any way to tell iTunes I only want to play songs that are on my internal hard drive?