Thank you for the response. I am NOT looking for songs that I simply have not played in iTunes. I AM looking for music files that are not even in the iTunes Library (aka: that I have never opened with iTunes).
I agree the best way to do this is with a Smart Folder by using the "Last Opened" criteria, but what do I put after that? There is no option called "Last Opened: NEVER". Would setting the criteria to "BEFORE [some early date]" include song files that have never been opened with any application? Thanks again for the help.