Many guitarists are familiar with the standard 12-bar blues progression (for this article only the major, or ‘dominant’, blues will be considered, however, many of the concepts may be used for minor blues progressions also).
As a form, 12-bar blues continues to function as a template, both for teaching purposes and for song-writing in many genres of music. This template is very adaptable and there are many variations on the basic progression. These variations range from the addition of one or two extra chords to different chords on almost every beat. While there are many books and other sources which list 12-bar progressions from basic to complex (Dan Hearle’s book Jazz/Rock Voicings for the Contemporary Keyboard Player lists seventeen such progressions) many simply leave the reader to then assimilate this information without any further explanation of why these extra chords work, and how they function within the form.
While this article will not cover every possible 12-bar blues variation it will explain why certain chords are added and what function they serve in the 12-bar context.
Probably one of the most common variations to a standard 12-bar blues is the addition of a ‘quick change’ in bar two.
The quick change preempts the move to chord IV in bar 5 and creates harmonic movement which helps to add interest to the harmonically static first four bars of the standard form.
Another method of creating harmonic interest in the first four bars is to change the tonic chord in bars 3-4 to a minor tonic.
This is possible through the use of mixture: changing the major third of a major or dominant seventh chord to a minor third creates a minor or minor seventh chord.
Mixture can also change the second bar of subdominant harmony in bar 6 from major or dominant, to minor.
Another common addition to a standard 12-bar blues is the flat-VI – V turnaround in bar 12.
The addition of the flattened chord VI is a further use of mixture: chord VI of the parallel minor is here being used in the relative major key.
The use of the flattened VI, immediately preceding chord V, emphasises the dominant and creates harmonic movement rather than the full bar of dominant harmony in the standard 12-bar progression.
In Jazz the 12-bar blues progression receives extensive harmonic modification, notably through the addition of ii – V – I progressions. In the example below, bar 8, which in the standard 12-bar form is typically the second bar of tonic harmony, now outlines chords which form a ii – V progression with the G minor seventh chord in bar 9.
The G minor seventh chord is also chord ii of an extended ii – V – I progression across bars 9-11.
This progression can be extended further by adding the following chords (this is the progression for Charlie Parker’s tune, Now’s the Time).
Here, the second bar of subdominant harmony typical in bar 6 of a standard 12-bar blues is changed to a B diminished seventh chord which proceeds to tonic harmony in bar 7. The B diminished seventh chord can be thought of as a passing chord which results purely from voice-leading between the subdominant harmony of bar 5 and the tonic harmony of bar 7.
The dominant chords in bars 7-8 proceed chromatically down to the D dominant seventh chord which resolves (V – I) to the G minor seventh in bar 9. Although these dominants can be heard as passing chords between the F and D dominant seventh chords they also form an embellished ii – V – I progression.
Here, the E dominant seventh chord in bar 7 is the secondary dominant of the A minor seventh which, as we saw earlier, typically precedes the D dominant seventh chord in bar 8. In this example, however, the A minor seventh chord has been transformed into an E flat dominant seventh chord through the use of mixture and a tritone substitution.
This progression can be extended further with the addition of a ii – V progression to the subdominant in bar 5.
And, with a I – VI – ii – V progression in bars 11-12.
It can be extended still further with a series of ii – V – I progressions leading to the ii – V progression already preceding the subdominant in bar 5.
Here, each I chord also acts as chord ii of the following ii – V – I group.
The ii – V – I progressions in bars 2-4 could alternatively be played as a series of dominant seventh chords which move through the circle of fifths.
Bars 9-12 can also be embellished using the so-called ‘Coltrane changes’.
Here the ii – V – I progression Gm7 – C7 – F7 is embellished through the addition of V – I progressions a minor third apart.
The Coltrane progression also outlines two augmented triads.
As was mentioned at the outset, this is only a fraction of the potential changes which can be added to a standard 12-bar blues progression. Remember, these examples can be mixed and matched so that, even from the relatively few examples discussed above, further examples can be created.