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Jazz Theory and Practice

Module 4 a, b, c The Turnaround, Circles of 5ths, Basic Blues

C. The Basic Blues

If you ask a dozen musicians, you’ll get at least a dozen answers to the question: What is “the blues”? It’s a style, it’s a scale, it’s a

character; it’s a sequence of chords. There are slow blues and fast blues, major blues and minor blues, 12-bar blues and 16-bar blues.

We’ll start with the harmony. The one common factor in almost all blues harmonic patterns (“riffs” etc.) is that the IV chord is always

there, and often the V chord isn’t. This is not necessarily true in most pop and jazz standards, in folk music, and most traditional classical

music, where the IV chord tends to have a more subordinate role.

In classical music theory we speak of a plagal progression (I � IV � I) and a plagal cadence (IV � I). The plagal cadence is usually an

extension added to the phrase; sometimes called a plagal extension:

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A plagal cadence often appears as an extension at the end of a blues piece, often with a freely improvised “cadenza” over the IV chord:

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There are many blues “riffs” that are simple plagal progressions; an entire blues chorus may be nothing but a single plagal progression:

I – IV – I Blues riff

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In the two previous examples there is another element which really is essential to the “blues character”. In both examples C7 is used as the

I chord, and F7 chord is used as the IV chord, introducing two notes

that don’t belong to the major scale (Eb and Bb). These are often

called “blue notes”. In these two examples the same chord functions (I, IV) could appear as either simple major chords, major-6th chords,

or major-7th chords, but it just wouldn’t sound “bluesy”. Years ago, in

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a series of TV documentaries called Omnibus, the conductor Leonard

Bernstein described “blue notes” as really notes “in the crack”… that is, quarter steps between two notes on the piano keyboard. Surely

enough, if you listen to a good blues singer, or blues horn player, the blue notes they produce are often closer to a quarter-step than a half-

step. The C7 and F7 chords in the example introduce blue notes on the 3rd and 7th steps of the scale; the third blue note is the flat 5th (or

raised 4th) step of the scale.

Back in Module 1 the blues scale was mentioned briefly, but wasn’t included in the “minor scale family” even though it is only one note

different from the minor pentatonic scale:

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If you look at this blues scale as an altered (greatly altered!) version

of a major scale, you will discover that it is missing the 2nd and 6th

steps, providing the “pentatonic flavour”, the 3rd and 7th steps are lowered (blue notes) and the third blue note is “sandwiched” into the

middle of the scale:

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The blues scale is not really part of the minor scale family, even

though it’s only one note away from the minor pentatonic. In a session, if a musician calls for a “Blues in C”, that means the chord

changes will be mostly in C major (often with C7 and F7, as in the examples above), but the melodic patterns (“licks”) will probably be

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drawn from a C blues scale. The blues scale, in fact, doesn’t really

belong to major or minor, but can be used in both modes. Notice, in the following example, that often E-natural and E-flat often clash at

the same moment. Leonard Bernstein suggests that this is the keyboard player’s way of approximating that quarter step that falls in

between!

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Even though the blues scale is the common source of melodic patterns

for the blues musician, it’s unusual to find a standard tune that’s written purely in the blues scale.

The basic 12-bar blues chord progression has hundreds of variations,

but there really is one basic architecture that is the source for all 12-bar blues variations, and it looks like this:

PLAGAL PROGRESSION ���� CADENTIAL PROGRESSION I IV I V I

(4 bars ���� 2 bars ���� 2 bars) (2 bars ���� 2 bars)

In simple musical notation, the chords might look like this:

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In the real musical world, the basic blues progression would almost never appear this way, but this is still the real “common denominator”

for all blues variations. Below are the two most frequent harmonic variations used at the end, as variations of the cadential progression.

The first one is the familiar II � V � I; the second variation interrupts the motion from V to I, using a plagal cadence IV � I. In traditional

classical harmony the V � IV � I cadence would be totally foreign to

the style; in the blues it works, because the plagal IV chord is so much a part of the blues character.

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It would seem only natural to want to break up the long tonic chord at the beginning. There are dozens of ways, but probably the most

frequent variation is to introduce a second plagal progression (a plagal progression within a plagal progression!):

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Until this point, the basic architecture of the 12-bar blues progression

has been shown with simple triads; in the real musical world this would seldom happen. Here is the previous example coloured with

seventh chords, and there is one more harmonic change in the 8th measure (A7) to initiate a circle of 5ths leading to the cadence.

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This example uses a walking bass, which is often used in a solo piano

version of the blues changes. Walking bass will be a major topic in Module 6. The dominant-7th chord in the cadential progression has an

extra colour note: #9 (written as Bb,not A#). This produces a chord

that has both a major and a minor third, approximating that note “in

the crack”— the blue note. #9 chords will be introduced in Module 5. This example is only a hint of the countless variations on the basic

blues progression, enough for another lesson in Module 5.

Something to listen to: There are thousands of examples of the basic blues harmonic structure in various genres: jazz, “rhythm and

blues”, rock, even in gospel and country music. Here are just a few examples:

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Empty Bed Blues. Bessie Smith, 1928. Listen carefully for the

version of the basic chord progression, and notice the “Call and response” dialog between the singer and the trombonist. There are

several classic blues by Bessie Smith on YouTube.

West End Blues. Louis Armstrong ensemble. (1955) A great YouTube video that includes a notated display of the trumpet improvisation, and

chord symbols.

Hound Dog. Elvis Presley. Classic “rockabilly”. Many of Elvis’ hits

were basic blues.

Blue ‘n Boogie. Charlie Parker and Dizzy Gillespie (1951). Be-bop style blues. Different harmonic colour (added-6th chords), hardly any

blue notes. The tune(head) is a major tetrachord.

Return to the menu, and try the PLAY/SING and WRITE exercises for

Module 4c