Three functions of the diminished chord
A diminished seventh chord (four notes a minor third apart, e.g. C#°7 = C# E G Bb) can be used in three ways:
- Ascending (passing) diminished: connects two chords with the bass rising by a half step. It is equivalent to a secondary dominant b9 without the root.
- Descending diminished: connects with the bass falling by a half step (e.g. Em7 – Eb°7 – Dm7). It has no dominant function: it is pure chromatic motion.
- Auxiliary (common-tone) diminished: embellishes a chord with which it shares the root (C°7 – Cmaj7). Often written C°7 but played with C in the bass.
Ascending in C major
| Motion | Diminished | Equivalent to | Bass |
|---|---|---|---|
| Cmaj7 → Dm7 | C#°7 (C# E G Bb) | A7b9 (V/ii) | C – C# – D |
| Dm7 → Em7 | D#°7 (D# F# A C) | B7b9 (V/iii) | D – D# – E |
| Fmaj7 → C/G | F#°7 (F# A C Eb) | D7b9 (V/V) | F – F# – G |
| G7 → Am7 | G#°7 (G# B D F) | E7b9 (V/vi) | G – G# – A |
The progression Cmaj7 – C#°7 – Dm7 – D#°7 – Em7 with chromatic bass C–C#–D–D#–E is a classic of swing jazz, gospel, and stride.
Descending
| Motion | Diminished | Bass |
|---|---|---|
| Em7 → Dm7 | Eb°7 (Eb Gb A C) | E – Eb – D |
| Am7 → G7 | Ab°7 (Ab B D F) | A – Ab – G |
| C/E → Dm7 | Eb°7 | E – Eb – D |
The bIII°7 (Eb°7) between iii and ii is the most common descending one (turnaround: Cmaj7/E – Eb°7 – Dm7 – G7).
Auxiliary (common-tone diminished)
- Cmaj7 – C°7 – Cmaj7: C°7 = C Eb Gb A. The notes E and G fall by a half step (Eb, Gb) and then return; A is an appoggiatura of the fifth. A sound from "1940s films," Broadway, the gospel ballad.
- On the V: G7 – G°7 – G7 (G Bb Db E), less common.
- The #IV°7 with tonic bass (F#°7/C) is another form of auxiliary on the tonic.
Cadential six-four
The classic IV – #iv°7 – I6/4 – V – I (F – F#°7 – C/G – G7 – C) is a passing diminished that leads to the cadential six-four: you find it in chorales, gospel, soul ballads, and standard endings.
Voice leading
- The note that rises by a half step (the bass C#) is the "leading tone" of the target: it must resolve upward.
- The diminished seventh (Bb in C#°7) falls by a half step (Bb → A, the fifth of Dm7).
- In the auxiliary diminished, at least one voice holds the common tone.
Diminished chord and symmetry
C#°7 = E°7 = G°7 = Bb°7: the same chord has 4 names. Every diminished seventh can therefore resolve to 4 different keys (see the card on enharmonic modulation) and, by lowering any one of its notes by a half step, it becomes one of the 4 dominants a minor third apart (B°7: lowering B → Bb7, D → Db7, F → E7, Ab → G7).
Exercise for the producer
- Piano (Piano V or Stage-73 V) at 80 BPM, 60% swing.
- Play | Cmaj7 C#°7 | Dm7 D#°7 | Em7 Eb°7 | Dm7 G7 |.
- Try the same progression in a different genre (lo-fi hip hop, 75 BPM, Rhodes with tape saturation): the passing diminished works outside jazz too.
Related topics
The diminished seventh chord and its uses, Barry Harris's diminished sixth, gospel harmony, enharmonic modulation, chromatic voice leading.