The ‘Blues Scale’ is basically the Minor Pentatonic Scale with a flat 5th note added. Wrong notes sound good in the blues, you can bend a note anywhere you want, but this one sounds particularly good. That’s the note between the 4th & 5th note, also called the ‘Blue Note’. If you’d like an example just listen to almost any Black Sabbath or AC/DC song.
A Blues Scale – 5th Position
E Blues Scale – Open Position