The 12-bar blues

Born in the American South in the late 19th century, the blues is the root of jazz, rock, soul and funk. Its most common form fits in 12 bars and three chords. Once it's in your fingers and your ears, you can play with musicians all over the world.

The form

All three chords are dominant seventh chords (C7 = C E G B♭). In classical music these chords "want" to resolve; in the blues they are the sound of home. The last bar (V7) sets up the next chorus: it's the turnaround.

A very common variant, the quick change: bar 2 moves to IV7 (F7) before returning to I7.

A simple voicing: third and seventh

The two notes that define a seventh chord are its third and seventh. Notice how they slide by a semitone between chords: E–B♭ (C7) becomes E♭–A (F7).

M:4/4
L:1/4
Q:1/4=90
K:C
"C7" [E_B]4 | "C7" [E_B]4 | "C7" [E_B]4 | "C7" [E_B]4 | "F7" [_EA]4 | "F7" [_EA]4 | "C7" [E_B]4 | "C7" [E_B]4 | "G7" [FB]4 | "F7" [_EA]4 | "C7" [E_B]4 | "G7" [FB]4 |]

The AAB lyric form

Blues lyrics often follow an AAB pattern: a line (4 bars), the same line over the IV (4 bars), an answer (4 bars). Your improvisation can do exactly the same:

M:4/4
L:1/8
Q:1/4=100
K:C
"C7" G2 _B c- c4 | z8 | G2 _B c- c2 _B G | E8 |
"F7" G2 _B c- c4 | z8 | "C7" G2 _B c- c2 _B G | E8 |
"G7" d2 d d- d2 B G | "F7" c2 c c- c2 A F | "C7" G2 E C- C4 | "G7" z4 D E G2 |]

Step-by-step exercise

1. Start the blues backing in C. Count the bars aloud ("one-two-three-four, two-two-three-four…") for two full choruses.
2. Left hand: play the root of each chord on beat 1. If you get lost, wait for bar 1 to come back in.
3. Right hand: play the third-seventh voicing above in a "Charleston" rhythm (beat 1, then the "and" of 2).
4. Play the AAB riff above, then invent your own 2-bar A phrase and apply the AAB scheme.
5. Repeat in F with the blues backing in F (F7 – B♭7 – C7).