Blues

The notes

C E♭ F G♭ G B♭, then C. Five of the six make up the C minor pentatonic; the G♭ sits between F and G and is usually played as a passing note rather than held.

The scale contains both the minor third and, in practice, an implied major third bent up from E♭ — which is why written notation never quite captures blues playing. The pitch lives between the two.

On the fretboard

The eighth-fret box with the root on the low E string is the standard shape, and it is the first thing most rock and blues guitarists learn to improvise with.

The flat fifth falls awkwardly inside the box, which is deliberate: it is meant to be passed through quickly or bent, not landed on. Players who hold it discover why it is called a blue note.

Where it is used

Over any chord in a blues in C — the scale works against C7, F7 and G7 alike, which is unusual and is the reason blues improvisation is approachable.

It also appears across rock, funk and jazz whenever a solo needs grit rather than sophistication. The same six notes, moved to another root, do the same job in every key.

The scale is also why a beginner can sound convincing in a week: six notes that fit every chord of the form remove the need to follow the harmony, and the ear does the rest.