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Lesson 4 - Blues progressions and the pentatonic scale

The "blues" is one of the most common jazz forms. It is usually (though not always) a twelve-bar progression with four bars on the I chord, two bars on the IV, two on the I, one bar on the V chord, one on the IV, ending with two bars on the I.

|I		|		|		|		|

|IV		|		|I		|		|

|V		|IV		|I		|(V)		|

The V chord is used in the twelfth bar as a turn-around chord if repeating the form. Very often the I, IV, and V chords are dominant seventh chords or any substitute chord which functions as a dominant seventh (see lesson 4 on Diatonic Chord Substitutions).

The blues progression presents an interesting problem in improvisation. Since each chord in blues is usually an dominant seventh, each chord is in a different key. Many improvisations on a blues progression do not change key, but rather use a scale in which all notes are acceptable. While you can very legitimately treat each chord in a blues as a V chord of a different key, another valuable approach is through the use of the pentatonic scale (1-2-3-5-6 of the major scale).

A pentatonic scale can be used very successfully over a blues progression in C. The pentatonic scale will work over the entire progression and eliminates the need for constant change of key center in improvisation. For an extremely effective blues use the pentatonic scale a minor third above the root of the I7 chord, i.e. use the Eb pentatonic scale over a blues starting on C7. The sound of this pentatonic is very bluesy and is great as an alternate sound to the pentatonic on the root on the I7. Use one scale and then contrast the other for the full effect of pentatonic blues.

The pentatonic scale is incredibly versatile and can be used to reduce the number of key centers needed in a great many progressions. When doubt of a situation try pentatonics.

The number of possible variations on the standard blues progression is endless. Consult the appendix for alternate blues progressions.

Pentatonic scale

Exercises

  1. Play the following progressions.
  2. Analyze each progression and determine key centers.
  3. Practice soloing ever these chord sequences by using a tape recorder to make a rhythm track or have a friend play the progression while you solo.

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