Watch the Flat Five online guitar lesson by David Hamburger from 30 Beginner Fingerstyle Blues Licks You MUST Know
The blues scale has all the same notes as the minor pentatonic scale – R, b3, 4, 5, b7 – with the b5 added. In the key of A, the b5 is Eb, that note we're grabbing at the fourth fret on the second string in this lick. Whether you look at the blues scale as its own thing or as a minor pentatonic scale with one note added is up to you. I do realize semantics isn't everybody's bag by a long shot.