Omnibus
Music Theory Resources
Harmonic Function
Roman Numerals and Scale Degrees for Major Keys
The omnibus is a wedge-shaped chromatic chord progression that encompasses all the notes of the chromatic scale.
Characterized by two voices moving in contrary motion (by half-steps), while the other two voices share common-tones (which change every four chords.
It is circular, the beginning and ending chords are identical
Based on a minor third chromatic mediant relationship.
There are always at least 4 voices
Goes through the minor-third key sequence, (ex. c-eb-f#-a)
Consists of two basic chords
German augmented-sixth chord
Minor tonic six-four chord
Typically has a descending bass line, and ascending tetrachords in the non-bass voices.
C G6
5 B♭7 Dm6
4 B♭4
2 G7 C
A more extended treatment of this version of the omnibus could be:
C G6
5 B♭7 Dm6
4 B♭4
2 G7 Bm6
4 G4
2
E7 G♯m6
4 E4
2 C♯7 Fm6
4 C♯4
2 B♭7 Dm6
4 B♭4
2 G7 C
Examples
Schubert's Piano Sonata in A minor, Op. 42, first movement, mm. 32–39
Brahms, Rhapsody in G minor, Op. 79, No. 2, mm. 13-15.
The second theme begins with a German augmented-sixth chord in the key of d-minor. It moves to a major-minor seventh chords on GBDF, which does not have a clear function in the key of d minor. The two chords share pitches D and F. Bb moves to B, G# moves ti G.
Tchaikovsky Piano Concerto No. 2, Op. 44: I:cadenza, mm. 394-416
Pathetique Symphony movement 1
Beethoven Symphony No. 2, Op. 21: I, mm. 326-340.
Use:
Can be used in whole or in part
Sometimes used as a prolongation of the dominant-seventh chord. In this case, the progression will consist of five chords, beginning and ending with the dominant-seventh chord.
Like the diminished-seventh chord, there are only three transpositions
Alternate version (Vogler)
substitutes a fully-diminished seventh chord for the inverted augmented0sixth chord, with the bass note of the augmented0sixth chords (the inverted seventh) as the root of the diminished-seventh chord.