The minor pentatonic with a bruise on it.
The Scale
The blues scale is the Minor Pentatonic with one note added — a flattened fifth wedged between the fourth and the fifth. That single chromatic passing tone, the notorious "blue note," transforms a folk-simple five-note structure into something that carries the whole emotional weight of the blues tradition. Its origins lie in the collision of West African tonal practice with European harmony in the American South, where singers bent pitches into the cracks between the piano keys. The written blues scale is a Western approximation of that bending: an attempt to notate a note that really lives in the gliding space between the third and the fourth, and between the fourth and the fifth.
Structure
| Attribute | Value |
|---|---|
| Notes (from C) | C E♭ F G♭ G B♭ |
| Interval formula | Minor pentatonic plus the ♭5 |
| Number of notes | 6 |
| Defining feature | The added "blue note" (♭5) gives it its ache |
Character
The added flat fifth is a dissonance, and that is exactly the point. Passed through quickly, it does not resolve so much as sob — it introduces an instability that the surrounding pentatonic notes then absorb, producing the scale's characteristic push-and-release, its sense of longing that never quite settles. The blue note is best used in motion rather than dwelt upon; lingered on, it turns sour, but brushed against it gives every phrase a catch in the throat.
In Practice
It is the defining melodic resource of the blues and everything the blues fathered — jazz, rock and roll, soul, funk, and their countless descendants. Guitarists slide up to the flat fifth and back; harmonica players bend into it; horn sections lean on it. Wherever music wants to sound like it is telling the truth about hard times, this scale is usually doing the work.