Blues scale

The term blues scale refers to several different scales with differing numbers of pitches and related characteristics.

The hexatonic, or six-note, blues scale consists of the minor pentatonic scale plus the ♭5th degree. A major feature of the blues scale is the use of blue notes, however, since blue notes are considered alternative inflections, a blues scale may be considered to not fit the traditional definition of a scale. At its most basic, a single version of this "blues scale" is commonly used over all changes (or chords) in a twelve bar blues progression. Likewise, in contemporary jazz theory, its use is commonly based upon the key rather than the individual chord. The evolution of this scale may be traced back to Asia (pentatonic major) through native North America (pentatonic minor) with the addition of the flat 5 blue note (slave trade/Africa).

Greenblatt defines two blues scales, the major and the minor. The major blues scale is C, D, D♯/E♭, E, G, A and the minor is C, D♯/E♭, F, F♯/G♭, G, B♭. The latter is the hexatonic scale (top).

The heptatonic, or seven-note, conception of the "blues scale" is as a diatonic scale (a major scale) with lowered third, fifth, and seventh degrees and blues practice is derived from the "conjunction of 'African scales' and the diatonic western scales". Steven Smith argues that, "to assign blue notes to a 'blues scale' is a momentous mistake, then, after all, unless we alter the meaning of 'scale'". It is the 2nd mode of the Harmonic Minor scale.

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