The blues scale is kind of a unique animal: half diatonic scale, half blue notes. Some people think that only the flat 3rd, flat 5th, and flat 7th of the diatonic scale is used in the blues, but that’s not the case. It’s the juxtaposition between the major 3rd and the minor 3rd, the perfect 5th and the diminished 5th, and the major 7th and the minor 7th that creates that facinating tension that creates the “blues” sound. The human voice can sing in the cracks between the major and minor 3rd, but that’s not the case with the piano — we are stuck with fixed pitches — so we need to create some tension between the two. Watch this short video and you’ll get the idea:

If you want more instruction on the blues, go to Playing The Blues on our online catalog of piano courses.