Formula
The diminished or octatonic scale has eight notes and alternates whole tones and semitones. It has two rotations:
- Whole-half (W-H): 1 2 b3 4 b5 b6 6 7. On C: C D Eb F Gb Ab A B.
- Half-whole (H-W): 1 b2 #2 3 #4 5 6 b7. On C: C Db D# E F# G A Bb.
There are only three different octatonic collections (on C, C#, D); it is Messiaen’s Mode 2. It expands on the overview in “Symmetrical scales: whole-tone and diminished”.
Properties
- Symmetry by minor thirds: transposed by 3, 6 or 9 semitones it remains identical. So C, Eb, F# (Gb) and A share the same W-H scale; the chords built on these four degrees are “equivalent”.
- Interval vector <448444> (8-28): very rich in minor thirds and tritones.
- It contains two diminished sevenths (C Eb Gb A and D F Ab B), four major triads and four minor triads (in H-W on C: C, Eb, F#, A major and minor), four dominant chords (C7, Eb7, F#7, A7).
Which rotation over which chord
| Chord | Scale | Why |
|---|---|---|
| C°7 (diminished) | C whole-half | the chord tones are 1, b3, b5, 6 (=bb7); the others are tensions a tone above |
| C7b9, C13b9, C7#9#11 | C half-whole | it contains b9, #9, 3, #11, 5, 13, b7: the dominant with natural 13th and altered 9ths |
| °(maj7) chord or passing °7 | whole-half |
Mnemonic rule: diminished → start with the whole step; dominant → start with the half step.
Color
Tense, kinetic, symmetrical, “modern”: suspense, chases, science fiction; in jazz, the “polished” dominant with b9 and 13. Unlike the altered scale, the H-W has the perfect 5th and the natural 13th.
Use in genres
- Russian classical and 20th-century classical: Rimsky-Korsakov (in Russia it is called the “Rimsky-Korsakov scale”), Stravinsky (Petrushka: the “Petrushka chord”, C major + F# major, is entirely octatonic; The Rite of Spring), Bartók, Messiaen.
- Jazz: 13b9 dominants (typical pianist voicings), symmetrical lines by Coltrane, Michael Brecker, Herbie Hancock; patterns that move by minor thirds.
- Soundtracks: suspense and action (string ostinatos on diminished sevenths, brass in major triads a tritone apart).
- Metal and progressive: octatonic and symmetrical riffs, widely used in technical metal.
Useful patterns and voicings
- Major triads a minor third apart (C – Eb – F# – A) over a C bass: all inside C H-W.
- C13b9 in 4 voices: E Bb Db A (3 b7 b9 13) with the bass C.
- Tritone pairs: C–F#, Eb–A as symmetrical “pivots”.
Melodies
- Repeated phrases shifted by a minor third are the trademark of the scale (symmetrical sequence).
- To leave the scale convincingly, resolve to a note of the next chord by semitone (e.g. C7b9 → F: Db → C, Bb → A).
Common mistakes
- Using the whole-half scale over a dominant: it puts the 4th and the major 7th against the 3rd and the b7.
- Using the H-W over a chord with a marked minor 13th (b13): you need the altered scale.
- Staying on the scale for a long time without an anchor: fine in a suspense cue, less so in a song.
Exercise
- Over C7b9 → Fmaj7 play C half-whole (C Db D# E F# G A Bb) and resolve to A or C.
- Sixteenth-note string ostinato over C°7 with the whole-half scale, for an action cue at 140 BPM.
- Program the “Petrushka chord” (C E G + F# A# C#) on a pad and hear how both triads belong to the same scale.
Related
Symmetrical scales: whole-tone and diminished; Messiaen’s modes of limited transposition; Diminished seventh chord; Altered chords; Hungarian major scale; Super Locrian bb7.