Definition
An enharmonic modulation uses a chord that sounds the same but is written (and interpreted) differently in the two keys. The pivot chord arrives with one function and departs with another. It works only in equal temperament, where G# = Ab, C# = Db, etc.
1. Diminished seventh
The diminished chord is symmetrical: its four notes can be read as four different vii°7 chords.
| Spelling | Notes | vii°7 of | Resolves to |
|---|---|---|---|
| B°7 | B D F Ab | C / Cm | C or Cm |
| D°7 | D F Ab Cb | Eb / Ebm | Eb or Ebm |
| F°7 | F Ab Cb Ebb | Gb / Gbm (= F#) | Gb or Gbm |
| G#°7 | G# B D F | A / Am | A or Am |
So a single diminished chord leads to 8 keys (4 major and 4 minor). Example: in C major, B°7 seems to prepare C; you reread it as G#°7 and resolve to Am (close) or as D°7 and resolve to Eb (distant).
2. German sixth ↔ dominant seventh
The German sixth in C (Ab – C – Eb – F#) sounds like Ab7 (Ab C Eb Gb).
- As a German sixth in C: Ab and F# move apart to G → it goes to G (V) → C.
- As Ab7 (V7 of Db): it goes to Db.
So: from C you go to Db in one step (or vice versa). The same sonority connects keys a semitone apart.
Example: C – Am – Fm – Ab7 (= Ger+6) – Db.
3. Augmented triad
C+ = E+ = G#+: three readings, three augmented dominants.
| Reading | Notes | V+ of | Resolves to |
|---|---|---|---|
| C+ | C E G# | F | F or Fm |
| E+ | E G# B# | A | A or Am |
| Ab+ | Ab C E | Db | Db or Dbm (C# minor) |
Useful for modulating by major third (hexatonic system).
4. Other enharmonic pivots
- Tristan chord / half-diminished: Fø7 (F Ab Cb Eb) = F B D# G# (“French sixth” reading): a bridge between Eb minor and A minor.
- Neapolitan: in C minor Db (bII) = C# major = V of F#: it leads to F# (tritone).
- Dominant read as a German sixth: in C, G7 respelled G – B – D – E# (E# = F) is the German sixth of B: it resolves to F# (V of B) and leads into B, a half step below C.
How to write it well
- Prepare the chord in the old key with a credible function.
- Hold it long enough to be heard (1–2 bars).
- Resolve decisively in the new key, ideally with an authentic cadence right after.
- In part-writing, change the spelling (Ab → G#) at the point where the function changes.
Examples
The diminished chord as a gateway to distant keys is a commonplace of Romanticism (Schubert, Chopin, Liszt, Wagner); the German sixth used as a dominant often appears in Schubert and Brahms to move to a key a half step higher. In pop, the same idea is found in half-step key changes prepared by a “double-meaning” dominant chord.
Producer exercise
- 4 bars in C: C – Am – Dm – B°7.
- Instead of going back to C, resolve B°7 to Eb (reading it as D°7): the last chorus goes up a minor third.
- Try the Ab7 variant: C – F – Ab7 – Db (chorus a half step higher), useful for a more elegant pop “key change” than the direct jump.
Related topics
Modulation techniques, diminished seventh chord, augmented sixth chords, augmented chords, chromatic and direct modulation.