Definition
The omnibus progression is a chromatic sequence in which two voices move by semitone in contrary motion (usually the bass and an upper voice) while the inner voices stay still. It alternates dominant seventh chords with six-four (or diminished) chords, and is used to prolong a dominant or to modulate smoothly. It is widely used in the late Romantic period (Schubert, Chopin, Wagner, Tchaikovsky, Mussorgsky).
“Divergent” version (prolongs G7 and leads to E7)
Fixed inner voices: B and D. The bass descends G → F# → F → E, the voice carrying the seventh rises F → F# → G → G#.
| Step | Bass | Inner voices | Moving voice | Chord |
|---|---|---|---|---|
| 1 | G | B D | F | G7 |
| 2 | F# | B D | F# | Bm/F# (six-four chord) |
| 3 | F | B D | G | G7/F (third inversion) |
| 4 | E | B D | G# | E7 |
The bass and the moving voice “swap” the notes G and F (voice exchange). Once at E7, the pattern can start again with the new seventh D rising and the bass E falling, reaching C#7 and so on (each cycle descends a minor third): in C, E7 leads naturally to Am.
“Convergent” version (from G7 to G7/B)
Fixed inner voices: D and F. The bass rises G → Ab → A → Bb → B, the upper voice falls B → Bb → A → Ab → G.
| Step | Bass | Inner voices | Upper voice | Chord |
|---|---|---|---|---|
| 1 | G | D F | B | G7 |
| 2 | Ab | D F | Bb | Bb7/Ab (third inversion) |
| 3 | A | D F | A | Dm/A (six-four chord) |
| 4 | Bb | D F | Ab | Bb7 |
| 5 | B | D F | G | G7/B |
The result prolongs the dominant G7 for five chords without ever leaving its “orbit” (the notes D and F always remain). One variant uses a diminished chord at step 2 (G#°7 = G# B D F, with three notes in common with G7), as Open Music Theory shows.
Why it works
- Contrary motion by semitone is the strongest and smoothest voice leading possible.
- The stationary voices ensure timbral continuity.
- The intermediate dominant seventh chords can be read enharmonically (for example as augmented sixths), so the progression can open doors to distant keys.
Real examples
- Schubert, Piano Sonata in A minor, D 845: in the transition to the second theme the bass descends chromatically in an omnibus progression.
- C. P. E. Bach, Rondo in A minor (W 56/5): a descent of a full octave.
- Wagner: in Tristan und Isolde and to characterize Kundry in Parsifal.
- Tchaikovsky, The Nutcracker: the scene in which the Christmas tree grows uses a “wedge” progression of this type to move from E minor to Bb.
- Chopin, Nocturne in Db major, Op. 27 No. 2: a variant with the diminished chord.
Use in composing for picture
The omnibus is perfect for suspense crescendos (tremolo strings, descending chromatic bass, rising brass): the listener feels the tension increase without knowing where it is going, until a clear dominant arrives.
Producer exercise
- Write the divergent version in the Piano roll, 1 chord per bar, 70 BPM.
- Assign the bass to double basses + cellos, B and D to the violas, the moving voice to the first violins.
- Continue the cycle for 8 bars (G7 → E7 → C#7 → Bb7 …) and then resolve to a tonic of your choice. Hear how each restart connects to the previous one.
Related topics
Chromatic voice leading, harmonic sequences, augmented sixth chords, Tristan chord, prolongation.