Pinch harmonics are a guitar technique that produces high-pitched, squealing sounds by lightly touching the string above the fret with the picking hand and then picking the string with the picking hand. This creates a harmonic node at the point of contact, which results in the high-pitched sound. Pinch harmonics are often used in rock, metal, and blues music to add excitement and aggression to solos and riffs.
There are two main types of pinch harmonics: natural and artificial. Natural pinch harmonics occur when the string is picked at a harmonic node, which is a point on the string where the string naturally vibrates. Artificial pinch harmonics occur when the string is picked at a non-harmonic node, and the picking hand creates the harmonic node by lightly touching the string above the fret. Pinch harmonics which are played using natural harmonics tend to have a brighter, more bell-like sound than harmonics played using artificial harmonics.