Tuning, Artificial harmonics and pinch style

ok i saw a guitarist tuning a guitar and he tuned way down by where you would do plain natural harmonics tuning but when he plucked the string he got a very high pitched noise, is this a way of tuning that i don't know of or was i hearing things? Second what is artificial harmonics and pinch style and how are they played?

An entire description and instructions are at http://cyberfret.com/techniques/harmonics/natural/index.htm
Cyberfret.com also has stuff on pinch & touch harmonics, but I've never really looked at it.