V. Chromaticism
The Omnibus Progression
Bryn Hughes
KEY TAKEAWAYS
The omnibus progression is a chromatic voice-leading technique that moves in contrary motion.
- The progression includes two voices that move participate in a voice exchange, while the other voices remain static
- This progression prolongs dominant harmony
- In the converging omnibus progression, the leading tone descends while the bass (which starts on the root) ascends
- In the diverging omnibus progression, the seventh ascends while the bass (which starts on the root) descends
- Both patterns can go through multiple iterations by “resetting” the progression when you reach another root-position dominant-seventh chord
The omnibus progression is a special type of chromatic sequence in which the bass and another voice in the texture move in contrary motion. The omnibus progression is most commonly used to prolong dominant harmony, but it can also be used as a means of modulating into distant keys.
There are two ways of writing an omnibus progression: with the bass and upper voices converging, or with the bass and upper voices diverging.
The converging omnibus progression
The converging omnibus progression begins on a root-position dominant-seventh chord. The bass moves upward by semitone, while the voice with the leading tone moves downward by semitone, creating a voice exchange. The voice leading in this progression should be as smooth as possible: The only voices that are moving are the ones involved in the voice exchange. The other voices remain static as common tones.
shows the prolongation of a dominant-seventh chord via a voice exchange between the leading tone (in the soprano) and the root of the chord (in the bass). Moving three semitones in this fashion brings you to another root-position dominant-seventh chord/German augmented-sixth chord (recall that these are enharmonically equivalent!). Moving four semitones in this fashion brings you to the same dominant-seventh chord on which you began the progression, but this time, in first inversion. The pattern yields five different chords, labelled 1-5 in the example below.
One variation of the omnibus progression that some composers use is to change the second chord in the pattern from a dominant-seventh chord to a diminished-seventh chord. In this version, there are three common tones held between the first and second chord. You can see this variation in
Brahms provides us with a good example of a converging omnibus progression. In
, we can see that the dominant chord in the key of B major is prolonged by way of an omnibus progression in mm. 38-41. Interestingly, he uses the progression again in mm. 46-48, this time to prolong the dominant of the new key of C♯, which is the key “implied” by the internal chords of the original progression in mm. 38-41.
The omnibus progression can be used to move into distant keys, and eventually traverse the entire octave (though in practice it is rare to go through the entire octave). Once you