blues scale
A six-note scale derived from the minor pentatonic with an added flattened fifth, creating the characteristic blue note
In Depth
The blues scale formula is 1-♭3-4-♭5-5-♭7, and in C it produces C-E♭-F-G♭-G-B♭. The added ♭5 (the blue note) creates a chromatic cluster around the fourth and fifth degrees that gives the blues its characteristic tension. The scale works over both major and minor chord progressions, which is unique among common scales. Blues players often bend notes between the scale degrees rather than landing cleanly on them, creating the expressive microtonal inflections that define the genre.
The blue notes in blues music do not correspond to any standard Western pitch — they exist in the cracks between the piano keys, which is why blues guitarists and singers bend notes constantly.