Ab Locrian

Character

Both the 2nd and the 5th are lowered. It starts on the seventh note of a major scale.

The lowered 5th is decisive. The chord built on the root is not a stable triad but an m7♭5. A scale whose centre cannot support itself is difficult to use as a tonal home.

So it is rarely used alone; it is used in passing. The most common application is over the first chord of a minor ii-V-i, when that chord is an m7♭5.

Metal sometimes uses that instability as the point. It is the scale to choose when you want a sound that does not resolve.

Scales with the same notes

This scale starts on note 7 of the A Major Scale scale and contains exactly the same notes. The fretboard positions are identical, so a shape you already know carries over.

Diatonic chords in this key

Seventh chords built on each scale note, using only notes from the scale. These do not clash with one another, so they are the reference set when you build a progression.

Practice

Hold an m7♭5 chord and play over it. That is the situation the scale actually occurs in.

It starts on the seventh note of its parent major scale, so you already know the fretboard shape. Only the root moves.

Linger on the first degree and the sound collapses. Practise treating it as a passing note.