Twelve-Bar Blues

The twelve-bar blues is a chord progression, and a song form, that lasts twelve bars and uses three chords: I, IV and V. In the blues they are usually all dominant seventh chords, so in C the chords are C7, F7 and G7. The pattern repeats for every verse or solo chorus, which makes it one of the easiest progressions to learn and play with other people.

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The standard pattern

C7 – C7 – C7 – C7 – F7 – F7 – C7 – C7 – G7 – F7 – C7 – G7

Think of it as three lines of four bars:

1. Bars 1–4: home, on I.
2. Bars 5–8: two bars of IV, then back to I.
3. Bars 9–12: V, IV, I, and a final V (the turnaround) that leads back to the beginning. On the very last chorus the last bar usually stays on I.

Traditional blues lyrics often fit this shape: a line in the first four bars, the same line repeated over IV in the next four, and an answering line in the last four.

Common variations

• Quick change: IV in bar 2 (C7 – F7 – C7 – C7 ...).
• V in bar 10: some blues stay on G7 for bars 9 and 10 instead of moving to F7.
• Jazz blues: jazz musicians add ii–V progressions and passing chords, while keeping the twelve-bar outline.

Why every chord is a seventh

In classical harmony a dominant seventh chord pulls toward a resolution. In the blues, I7, IV7 and V7 are colors in their own right; the flat seventh on each chord matches the "blue" notes of the melody and the blues scale. That is why C7 can be the home chord and still sound settled.

Playing it

Count the twelve bars aloud while you play the chords, so you always know where you are. Then add a left-hand shuffle (C–G, C–A in each bar) and improvise in the right hand with the C blues scale. The 12-Bar Blues gives you the pattern and grooves to practice, and The Pentatonic & Blues Scales gives you notes to improvise with.