Hey. Never heard the term "sympathetic" harmonics either. There are quite a few techniques used for creating harmonics. Pinch harmonics are where you use your thumb and dig into the strings to create a high pitch squeal. Because this technique works best with distortion you will hear them in metal and heavy rock guitar solos most often. If you think of all those squeal sounds people like Steve Vai use all the time then that is what they sound like.

Hope that helps. I have a whole lesson on the different types of harmonics you can use here

http://www.guitarstatic.com/lessons/other/harmonics.html :)