The 12-bar blues: I–IV–V
The 12-bar blues is a chord progression of three chords, I, IV and V, over twelve bars in a fixed order: four bars of I, two of IV, two of I, then V, IV, I and a last V that turns it around. In C that is C7, F7 and G7, and it is the form under the blues, early rock ’n’ roll and a lot of jazz.
Hear it in any key, in five styles
- I7C7
- I7C7
- I7C7
- I7C7
- IV7F7
- IV7F7
- I7C7
- I7C7
- V7G7
- IV7F7
- I7C7
- V7G7
Pick a key and the chord names change; pick a style and the drums, bass rhythm and chord rhythm change while the chords stay the same. The chords are C7, C7, C7, C7, F7, F7, C7, C7, G7, F7, C7, G7, one bar each. The link in the address bar keeps your key and style.
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Mood without music theory. The course’s harmony chapter builds chords, major and minor, keys and colour notes by ear. Unit 1 is free with a Google sign-in.
Pick up where you left off
Carry on with Unit 1; chords and progressions come in Unit 4: Harmony.
How it works
Think of it as three lines of four bars. The first line stays home on I. The second moves to IV for two bars and comes back. The third is the turnaround: V, IV, back to I, and a bar of V that pulls the whole thing round to the start. Singers often sing a line, repeat it over the IV, and answer it in the last four bars.
Every chord is a dominant seventh: C7, F7 and G7, each a major chord with a flat seventh on top. In a major key only the V7 belongs; the other two are bent, and that rub between major and flat is the sound of the style. The numerals say so with a 7: I7, IV7, V7.
Blues is usually played with a shuffle, every second note late. The styles below play it straight, in five genres, to show the form underneath; the chord strip lays the twelve bars out in three rows of four.
The 12-bar blues in every key
The numerals stay the same; only the letters change. The relative minor, in brackets, shares the same chords. Each chord is listed once; the strip above shows the order, bar by bar. The highlighted row is the key playing above.
| Key | I7 | IV7 | V7 |
|---|---|---|---|
| C major (Am) | C7 | F7 | G7 |
| G major (Em) | G7 | C7 | D7 |
| D major (Bm) | D7 | G7 | A7 |
| A major (F#m) | A7 | D7 | E7 |
| E major (C#m) | E7 | A7 | B7 |
| B major (G#m) | B7 | E7 | F#7 |
| F# major (D#m) | F#7 | B7 | C#7 |
| Db major (Bbm) | Db7 | Gb7 | Ab7 |
| Ab major (Fm) | Ab7 | Db7 | Eb7 |
| Eb major (Cm) | Eb7 | Ab7 | Bb7 |
| Bb major (Gm) | Bb7 | Eb7 | F7 |
| F major (Dm) | F7 | Bb7 | C7 |
Songs built on it
A few well-known examples, named so you can go and listen for the pattern. Nothing from them is reproduced here; the loop above is Swung’s own.
- Johnny B. Goode, Chuck Berry
- Hound Dog, Big Mama Thornton
- Rock Around the Clock, Bill Haley & His Comets
- Pride and Joy, Stevie Ray Vaughan
- Sweet Home Chicago, Robert Johnson
Common in blues, rock ’n’ roll, boogie-woogie, jazz and rockabilly.
What each style changes
| Style | BPM | Drums, bass and chords |
|---|---|---|
| Pop | 104 | bass: root eighths; chords: piano |
| House | 124 | bass: off-beat; chords: stabs, seventh chords |
| Lo-fi hip hop | 82, 58% swing | bass: with the kick; chords: electric piano, ninth chords |
| Trap | 140 | bass: 808; chords: dark pad |
| Reggaeton | 95 | bass: 3-3-2; chords: pad |