The seventh mode of Harmonic Minor is known as Altered Diminished. If you’re masochistic you can also call it Super Locrian ♭♭7. It is also called Diminished Whole-Tone. It is very dissonant and tense, a great choice for jazz and fusion.

Scale formula

The formula for the Altered Diminished mode is:

 1 - b2 - b3 - b4 - b5 - b6 - bb7

The ♭♭7 (which is enharmonically a major 6th) creates even more instability than found in the Altered Scale, which is derived from Melodic Minor.

Chords

• Dom7 Altered

Since Altered Dominant is built on the 7th degree of the Harmonic Minor Scale, it fits best over altered dominant 7 chords (V7alt) that resolve to a minor tonic.

Usage

The Altered Dominant Scale, also known as Super Locrian, Diminished Whole-Tone, or Locrian ♭♭7, is the 7th mode of the Harmonic Minor Scale. It is an extremely tense and dissonant scale, used heavily in jazz, fusion, and modern classical music for improvising over altered dominant chords (V7alt).

This mode is similar to the Altered Scale (from Melodic Minor), but with a distinct sound due to the minor-derived harmonic structure.

In Jazz & Fusion it is used over V7alt in ii-V-i progressions. In bebop in particular, musicians like Charlie Parker and John Coltrane use the Altered Dominant scale to play “outside” and create tension.

Progressive metal bands use Altered Dominant for dark, unsettling passages over V7alt chords.

Altered Dominant is also a great choice for horror, suspense, and thriller soundtracks.

Unresolved dominant chords using this mode create an uneasy feeling.