After hearing the lead guitar skills of Zakk Wylde I wondered how a guitar could be made to squeal on command. After a small amount of research, I quickly discovered that Zakk Wylde uses the pinch harmonic effect to generate radical sound changes. Apparently, the pinch harmonic technique is one of the most difficult guitar techniques to master. Yesterday, I was trying to figure out how to produce the electric guitar pinch harmonic effect.
Apparently, a pinch harmonic is an electric guitar technique requiring extensive overdrive and the application of a localized dampening effect. The electric guitar pinch effect can occur anywhere along the fretboard except with an open string. Immediately after striking an electric guitar string, apply a dampening effect to create the electric guitar pinch harmonic effect. Apply a dampening effect by gently scraping the side of the thumb on the string immediately after the pick touches the string. If you cannot produce a unique sound with your thumb, then strike the string with the pick and then lightly tap the string with the pick a second time to simulate the effect. The localized dampening effect should reduce the vibrations of the string canceling out part of the fundamental vibration of the string allowing the expression of a harmonic vibration. Apply the dampening effect at different points along the string between the end of the fretboard and the bridge.
I enjoy learning guitar techniques in the same way a trading card enthusiast enjoys collecting cards. During the course of learning about the pinch harmonic technique, I ended up playing the electric guitar unplugged. Even with the guitar unplugged, I was able to generate the pinch harmonic effect. Unplugged the guitar does not generate the wicked squeal associated with the pinch harmonic effect, but you can hear a radical change in string vibration. Without a proper guitar effects package playing an electric guitar unplugged might be the only way to began learning the pinch harmonic technique.