Blues
The twelve-bar form, dominant seventh chords, the blues scale and the shuffle feel.
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Content under musical review. It may contain inaccuracies.
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The twelve-bar form, dominant seventh chords, the blues scale and the shuffle feel.
Applied
Blues grew out of African American communities in the southern United States in the late nineteenth and early twentieth centuries. Rock, soul, funk and much of jazz draw from it. Musically you recognise it by a very stable form, dominant seventh chords on almost every degree and a melody that plays between the major and the minor third.
The three chords of a blues in A, all with a minor seventh:
And the A blues scale, which is the minor pentatonic plus a passing diminished fifth:
String 6, Fret 5: A2 · 1 · Root
Load the twelve bars and play over them with the scale. Try to end each phrase on a tone of the chord that's sounding:
Twelve-bar blues in A A blues scaleThe most common form is the twelve-bar blues:
| Bars | 1–4 | 5–8 | 9–12 |
|---|---|---|---|
| Chords | I7 · I7 · I7 · I7 | IV7 · IV7 · I7 · I7 | V7 · IV7 · I7 · V7 |
Frequent variants: the quick change (IV7 in bar 2) and the turnaround in the last two bars, which leads back to the top.
Characteristic features:
Over the I7, combine the minor pentatonic with the major pentatonic on the same root. A common move is to play the minor third and push it up a half step to the major third with a hammer-on or a short bend. Over the IV7, the minor third of the I is the chord's seventh, and it sounds especially good.
Levine describes how jazz reharmonises the form: a ii–V into the IV in bar 4, a passing diminished chord in bar 6 and a ii–V–I in bars 9 and 10 instead of V7 – IV7. The twelve-bar form stays, but each bar may carry two chords and demands following the changes with target tones.