What is a (natural) harmonic?
A natural harmonic is a musical note played by preventing or amplifying vibration of certain overtones of a guitar string. They are usually played by lightly placing a finger on a string at a nodal point (where the string is divided in ½, ¼, etc.). When picked, the string vibrates at a higher frequency than the fundamental tone causing a higher pitched overtone.
What is a pinch harmonic?
A pinch harmonic is a guitar technique in which the player's thumb or index finger on the picking hand slightly catches the string at a nodal point near the pickups after it is picked which cancels the fundamental tone of the string, and lets one of the overtones dominate. The result is a high pitch squeal.
Step 1: Amp or Pedal Settings
Turn up the gain on your amplifier or use a distortion pedal.
(Note: The more distortion, the easier it is to play a pinch harmonic.)