The 12-Bar Blues

In C major

C7 – F7 – C7 – G7 – F7 – C7 — rolling, conversational, endlessly extensible, around 108 BPM.

1. Bar 1 I7 C7
   C · E · G · Bb
   ▶ Hear it
2. Bar 2 IV7 F7
   F · A · C · Eb
   ▶ Hear it
3. Bar 3 I7 C7
   C · E · G · Bb
   ▶ Hear it
4. Bar 4 V7 G7
   G · B · D · F
   ▶ Hear it
5. Bar 5 IV7 F7
   F · A · C · Eb
   ▶ Hear it
6. Bar 6 I7 C7
   C · E · G · Bb
   ▶ Hear it

Why it works

Every chord is a dominant seventh, including the tonic — which is theoretically impossible in common-practice harmony and is exactly what makes it blues. The flattened sevenths come from the melodic tradition rather than from functional voice leading, so the chords sit still while the tension lives in the scale played over them. The form itself is a question, a repeat of the question, and an answer, mapped onto four bars each.

Where you'll hear it

The most useful twelve bars in music. Learn the standard turnaround in the last two bars and you can sit in with almost any band.

I7–IV7–I7–V7–IV7–I7 in every key

The same progression transposed. The roman numerals never change — that is the whole point of writing progressions this way.

Related progressions

• I7–IV7–I7–IV7–I7–V7–IV7–I7 The Quick-Change Blues
• i7–iv7–i7–V7 The Minor Blues
• I–IV–V The Three-Chord Progression