Barry Harris likes to say that the dominant chord got its name because it dominates everything in music. In conventional modal jazz theory, just about every chord derives from the major scale and its modes or the melodic minor scale and its modes. The scale associated with the dominant chord in the modal system is the Myxolydian mode of the major scale. Because it corresponds to the dominant 7th chord, I call this scale the dominant scale. I'd like to show you how just about any chord used in jazz can be derived from the dominant scale - and how you can use this way of thinking to create voicings and improvisational approaches you might not otherwise have discovered.

But first, let's take a look at where the dominant scales themselves come from in this worldview. At the root of everything lies the chromatic scale, shown on the top staff, with enharmonic equivalents (i.e., different note names representing the same pitch, such as D sharp and E flat). Separate the solid and hollow noteheads, and you've got the two whole-tone scales (middle staff). Each whole-tone scale contains three tritone intervals (diminished 5th or augmented 4th); take one tritone from each whole-tone to create the three possible diminished 7th chords (bottom staff).

Each diminished 7th chord in turn yields four dominant 7th chords. Pick a chord tone and lower it one-half step: This note becomes the root of the new dominant 7th chord. The dominant 7th chords shown here are all derived from the C sharp diminished 7th chord, and therefore share a relationship that we'll exploit later in the article.

Each dominant 7th chord has its associated dominant scale, and these scales are in turn related and interchangeable in the context of creating voicings and lines. Here is the C dominant scale (a), and three of the chords that it contains: C7, Em7 flat 5, and Gm7. All of these chords, as you'll see, can be used as voicings where a C7 is called for. In some progressions, minor 7th chords imply the major scale (b); I think of these chords as coming from the third degree of the major scale.