VI. Jazz
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Bryn Hughes and Megan Lavengood
Key Takeaways
- Blues harmony differs from tonal and jazz harmony in a number of important ways, especially in the treatment of the dominant seventh chord.
- In a standard 12-bar blues, all chords are dominant seventh chords.
- The blues is a schema that can have many alterations without ceasing to qualify as “a blues.”
- Common variations on the 12-bar blues are the 16-bar blues, the minor blues, and the jazz blues.
- The jazz blues blends jazz and blues harmonic languages together.
The blues is an extraordinarily important genre in U.S. popular music. Not only is the tradition itself very old, with roots reaching back to the music of enslaved African Americans, but it continues to exert influence on 21st-century popular music.
The documentation on the history of the blues is quite limited due to its age, but the earliest blues songs existed in the late 1800s, and it seems to have grown out from earlier African American musical styles, such as field hollers and work songs, as well as microtonal and rhythmic characteristics of West African music. In this sense, although jazz musicians very frequently play the blues, the blues as a tradition has distinct origins from jazz. Jazz developed first in New Orleans through a mix of African, Caribbean, and European influences. The result of this distinction is that many of the truisms of jazz or tonal music do not hold true in the blues. Among the biggest harmonic differences are:
- Dominant-quality seventh chords can have any function (tonic, dominant, or subdominant).
- Plagal cadences provide structural closure, instead of authentic cadences.
- Major and minor thirds are freely mixed together, and even used simultaneously (sometimes written in chord symbols as a major/dominant chord with a ♯9 extension).
This chapter introduces some of the most common forms of the blues encountered in the 20th and 21st centuries.
12-Bar Blues
The blues is a schema: a frame of reference for understanding lots of different chord progressions. Blues progressions can all be understood as outgrowths from a basic prototype.
The 12-bar blues progression is composed of three phrases, typically four bars each. A major difference between the blues and more traditionally tonal music is that it emphasizes plagal cadences instead of authentic cadences. At its most basic, the harmony progresses as shown in :
- The first phrase is entirely tonic harmony (I).
- The second phrase contains two bars of subdominant (IV) and two bars of tonic (I).
- The final phrase begins with one bar of dominant (V) followed by one bar of subdominant (IV) and two bars of tonic (I).
- All chords are dominant seventh chords and do not fit into a single key.
https://musescore.com/user/32728834/scores/6595108/embed
This is the simplest version of the 12-bar blues, but innumerable variations exist upon these changes. One of the most common additions is that the second bar may move to IV, then return to I in the thir