The blues scale

The blues scale is a minor pentatonic with one added chromatic note, the blue note (flat fifth). In C: C – E♭ – F – F♯ – G – B♭ – C. Played over dominant seventh chords it creates that bittersweet rub which is the soul of the blues.

M:4/4
L:1/8
Q:1/4=90
K:C
C _E F ^F G _B c2 | c _B G ^F =F _E C2 |]

The clash of thirds

The E♭ of the blues scale against the E of the C7 chord: in theory, a "wrong note". In the blues, it's exactly the point. Pianists imitate singers and guitarists who "bend" the note: you slide from E♭ to E.

M:4/4
L:1/8
Q:1/4=90
K:C
"C7" _E/=E/ G c _B G ^F =F _E | C8 |]

The major blues scale

Brighter: C – D – E♭ – E – G – A – C (major pentatonic + E♭). It's the sound of happy blues, gospel and country.

M:4/4
L:1/8
Q:1/4=100
K:C
"C7" C D _E =E G A G E | "C7" G2 E C- C4 |]

Mixing the two

The best blues players alternate: major colour over the I chord (E natural), minor colour over the IV (E♭ is the seventh of F7, so it's perfectly at home!). Hear the difference:

M:4/4
L:1/8
Q:1/4=100
K:C
"C7" E G A c- c2 A G | "F7" _E F A c- c2 _B A | "C7" G E D C- C4 |]

Step-by-step exercise

1. Play the C blues scale up and down, RH fingering 1-2-3-4-1-2-3-4 (thumb on C and G), until you can do it with your eyes closed.
2. Start the blues backing in C. For one chorus use only C, E♭ and F. Then add G, then B♭, then F♯ as a passing note.
3. Play the "bend" lick (E♭→E) at the start of each line (bars 1, 5, 9).
4. One chorus in the major blues scale, one in the minor blues scale, one mixing both.
5. Transpose to the blues in G: G – B♭ – C – C♯ – D – F.