Here's a fast one one that mostly uses the Phrygian-dominant mode. It’s in the key of C.
I start with a C power chord as a pickup to the first bar. Sometimes I like to include another fifth below the chord itself.
This brings out overtones that give the illusion of a lower root note, especially when you’re using heavy distortion. Even though the tempo marking is shown as "Freely," the lick is meant to be played as fast as you can.
So in bar 1, I ease into it by starting off relatively slow and move into full speed by the third beat, sort of what it would sound like if a snowball started rolling down a steep hill and got larger and faster on the way down. I like the Phrygian-dominant mode because of its exotic Eastern flavor; you can also think of it as a harmonic minor scale, which in this case would be in the key of F and starts on the fifth scale degree (C).
Notice how I play most of bar 1 legato—there’s nothing wrong with making it easy on yourself. At the end of bar 1 going into bar 2, I go into a series of five sextuplet patterns that gradually descend the neck. The fretboard shapes are a bit more familiar—the first two are minor (C minor and Bf minor), the third is major with an added s4—Af(#4)—and the last two return to minor (F minor and C minor).
“By the time I get to the third bar, the C minor tonality is firmly established and I riff all the way through until the last beat, where I downward sweep a quick F#• arpeggio (I upstroke the seventh at the end). I use this to lead into the end, which is a bluesy run based on C9 and incorporates the very familiar blues box pattern.”