Thanks
My internal hard drive is also getting crowded with TV shows and movies and I found this thread searching for a solution. To test your good advice before investing in an external drive, I tried using a memory stick. What I found was that the solution is actually simpler than I thought. I moved the song I wanted onto the stick in a folder structure [stick] > iTunes Music > [Artist] > [Album] > [Song], deleted it entirely (had to empty the trash, too) from [My name] Music > iTunes Music ... etc and then found the song in my iTunes library through the iTunes application and told it to play. It popped up "can't play it because it can't be located; would you like to locate it?" So I showed it where to find it on the stick, and it played fine. The coolest part is that after ejecting the stick, quitting iTunes, and starting everything back up again, it can now find the song fine without being told. I tried making an alias and did not have success with that. I tried just dragging it onto the stick but that copied the file instead of moving it, maybe a full on external drive would be different. I did drag it to different places on the internal drive and iTunes followed it wherever it went.
Thanks for your help. I just wanted to support any averagely savvy folks like me that it can be done and it's not complicated. Thanks Apple.