You might accidently play pinched harmonics sometimes, when your hand takes on a different angle.
In fact the best way to try this is to screw around with your angle of attack, holding the pick, barely sticking out of your fingers and see what happens...
It's all about the quick sequence of hitting the string with the pick then immediately (and briefly) have the string contact with your finger. This is what creates the squeeling sound.
You can also change the pitch of the squeal on the same fretted note by moving your hand position back and forth between the neck pickup
and the bridge. Lotsa fun! [img]images/smilies/icon_jam.gif[/img]