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This metal lick starts with a basic minor-pentatonic pull-off run on the high E and B strings (tuned down to D and A, respectively, since we're in standard tuning down one whole step).
When I get to the third beat of bar 1, I begin a cascading chromatic descent, wherein I slide my fret-hand index finger down the B string one fret at a time, with my ring finger simply following along on the G string, two or three frets up.
For maximum metal effect, I like to play the last note of the lick as a pinch harmonic (P.H.), to which I apply a wide finger vibrato.
The tempo is 158 beats per minute, 120 for slow practice.