C Locrian, Mapped for the Bass

C Locrian runs 7 notes to the octave, laid across this seat's EADG fretboard with every C marked. A blues phrase is short and keeps coming home to one pitch; the marked notes are where it comes home to.

The most dissonant, unstable mode — the tonic chord is diminished (b5), making a true Locrian tonal center rare. Used for color and passing harmony.

Heard in: Metal riffs, jazz (half-diminished ø7 chords in ii°7 – V – i), horror and tension film scores.

On the bass a scale supplies the notes between one chord and the next — the steps a line takes on its way to the change — far more often than it is played as a run.

Whatever scale you start from, the blues bends it: the third and the seventh get pushed flat, or somewhere between flat and natural, and that pull against the chord underneath is most of what the idiom sounds like.