Harmonics are harmonics - we have to thank Pathagoras for the mathematical theory behind them. If you pick the string at the right spot above a fretted note (and hit it with your thumb, 12 or 24 fret lengths above) you'll get a harmonic - often called the pinch harmonic. If you tap a spot above a fretted note (12 or 24 etc) you'll get a harmonic - often called tapped harmonics. Not real sure where they came up with artificial harmonics...it's either a harmonic or not.
-Bob
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