Watch the Microtonal Expressions online guitar lesson by Andy Aledort from 30 Beginner Slide Blues Guitar Licks You MUST Know
This lick is titled "Microtonal Expressions" because throughout the lick the slide is moved in very small increments (less than a half step) in order to provide more of a vocal-type feel and musicality to the sound of the notes. Building on the previous licks in terms of ramping up the complexity, this lick begins with two notes sounded on the first string, but the next three eighth notes are played on three successively lower strings, so you'll have to deftly move across the strings with clarity and precision.
Another element to look out for is the manner in which I move either up to or down to the notes in constantly alternating fashion as the lick progresses. The phrase ends by first sounding an E root note and then gently pulling the slide back, or flat, about a quarter tone, followed by a vibrato, closing the phrase with a vocal-like timbre.