Review: Variations of the Dominant Seventh Chord

The chord set below shows the chromatic variations of the dominant seventh chord.

Ways to alter dominant seventh chords:

1. By lowering the 5^th of the dominant seventh chord to create .
2. By augmenting the 5^th of the  dominant seventh chord to create . (Covered in the chapters on Augmented Triads and Augmented Dominant Seventh and the Augmented Sixth Chord.)

Altering V⁷ to Create

The dominant seventh chord with a flat 5^th is modeled after the root position French sixth chord (/V).

Review: The Fr⁶ chord

The French sixth chord is the most dissonant chord in music of the Common Practice Period due to the two interlocking tritones that produce three tendency tones, each of which must resolve: the A6 (le – fi) resolves outward and the 7^th of the chord (do) resolves down to ti.

Altered dominants based on the Fr⁶ chord model (dominant seventh chord with a flat 5^th )

The same resolution of tendency tones in the Fr⁶ chord applies to:

1. The  chord in root position.
2. The   chord in second inversion.
3. Any   secondary dominant.

The most frequently used version is the   chord in second inversion, with the flat 5^th in the bass (as with the French sixth).

Common uses of the dominant seventh chord with a flat 5^th

In major keys:

*The use of altered dominant seventh chords in minor keys is limited to /iv and /V.

Dominant seventh chords with a flat 5^th are used most often in second inversion.

Voice Leading

1. Dominant seventh chord with a flat 5^th in second inversion
2. Dominant seventh chord with a flat 5^th in root position
3. Root position Fr⁶: /V

Note that the diminished 5^th is usually approached and left by a half step.

4. Dominant seventh chord with a flat 5^th as a secondary dominant of vi
5. Dominant seventh chord with a flat 5^th as a secondary dominant of ii and I

The extended line after mi in the alto of example 4 and after la in the alto of example 5 indicates held or repeated notes.

6. Dominant seventh chord with a flat 5^th used as a secondary dominant in a chromatic sequence

Here is the chromatic secondary dominant sequence withV chords:

Compare example 6a above to the diagram below.

Note that every other chord has been altered into a Fr⁶ type of a secondary dominant (V /x) with the flat 5^th in the bass, thereby creating a chromatic scale in the bass.

review:
Resolution Tendencies of the French Sixth Chord as a dominant