A Locrian on Guitarrón

A Locrian runs 7 notes to the octave. Below it is mapped onto this instrument's A–D–G–C–E–A fingerboard with every A marked, because what a player needs mid-number is not the pattern but where the root is when the harmony moves under it.

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.

The bass takes almost no melodic line, and that is precisely why these matter: the notes between one root and the next come out of a scale, and an approach that lands wrong is the loudest wrong note in the ensemble.

Take it slowly against the playback until the geometry stops being geometry, then put it under a number in A minor and let the written line pick its own notes out of it.