Watch the Play the Harmonic Minor? Why, Yes, Yes You Can! online guitar lesson by Jeff Scheetz from Blues Jam Survival Guide
When we have that flat 6 Major chord and the 5 Major, we can say we are in harmonic minor instead of our natural minor. The difference is that the harmonic minor scale has a natural 7 while the natural minor has a flat 7 in it. Rarely will you be playing the harmonic minor scale over a standard blues song, but this one fits so perfectly that it is hard to resist. Just keep a watch out for the blues police.