Written by Edward Cupler
The Pentatonic minor blues scale can be thought of as an extended version of the Pentatonic minor scale. The only difference between the two scales is the addition of the flatted 5th note. This additional note is also referred to as the blue note and sometime it's referred to as the Devils note. Whatever you call it, the flat 5th adds a great deal of expressiveness to the Pentatonic guitar scale. You can hear it used by guitarists such as Tony Iommi, Randy Rhoads, George Lynch and a host of other guitar players too numerous to mention here.
Note: The following guitar scale examples begin on the 5th fret and are in the key of A minor.