Octatonic/Diminished Scales

Octatonic scales

An octatonic is a scale of 8 notes (thus octatonic = 8 tones) that have alternating half and whole steps between the notes.

There are 2 scales that are comprised of half then whole steps (before the notes start repeating):

There are two scales that that are comprised of whole then half steps (before the notes start repeating):

Diminished scale

These scales are also called diminished scales since the chord that is formed by every other note is a fully diminished 7th chord.

The chord created by the notes in the octatonic scales form fully diminished 7th chords. You can see there are two fully diminished 7th chords formed by each scale:

The chord formed by the notes in purple below form a B fully diminished 7th chord.

Knowing that these scales contain fully diminished seventh chords is helpful when improvising since, if there is a fully diminished 7th chord in a piece – for example, a B-(b5b7) — you can use the C whole-half octatonic scale to improvise on this chord.

Exercises:

Play octatonic/diminished scales on your instrument.

Improvise on the notes in a particular octatonic/diminished scale.

Write a progression including fully diminished 7th chords. Then improvise on the chords in the progression, using octatonic/diminished scales on the fully diminished 7th chord.