It’s an impressive, sparkly sound, and the simplest way to achieve it is to crank the distortion way up and play a repeated three-note pull-off lick involving an open string [Ex. 1]. The key is muting the string—or even multiple strings, if that’s easier—with a picking-hand finger (or the edge of the picking-hand palm) and gradually sliding it along the string away from the bridge and toward the nut. As you slide, repeat the fully legato (i.e., entirely slurred, not picked) fretting-hand lick over and over, and the harmonics should change in pitch and timbre. Try out different muting approaches until you find the one that fires off the brightest, most colorful and articulate array of partials. (I find my middle finger generally works great for these machine-gun style harmonics, especially if I start somewhere between the bridge and neck pickups.)
Unfortunately, when it comes to generating these sounds, most guitarists never get past licks like Ex. 1. There are many different harmonic sprays you can get if you experiment. For instance, move to a wound string and a whole new sound radiates [Ex. 2]. Or, expanding on that, repeatedly ascend and descend the first six notes of a three-note-per-string G major scale [Ex. 3]. And finally, moving back to the third string, here’s a really sick one that I just love [Ex. 4]. The fretting hand repeats an eight-note lick while the picking hand middle finger—this time just the tip of that
finger—mutes the string at the 9th fret. Then, I shift the muting finger up to the 10th fret, which totally changes the harmonics. You just gotta hear this stuff, so click on over to guitarplayer.com and I’ll play these examples and many more for you via downloadable mp3.