Lesson 29 Secondary dominant of the mediant and submediant

Lesson 29 Secondary dominant of the mediant and submediant

Part I - Introduction 

The secondary dominant of the mediant and submediant are found almost exclusively in Major Keys.  This is because of the chord qualities of each chord in the minor key.  the III can be either Major or augmented.  The vi chord can be either major or diminished.  the III⁺ can not be used as a tonic because it is not major or minor.  The Major III is an acceptable tonic.  In C Major, the dominant of the III would be spelled: B- D#-F#.
Here is the V⁶/vi and V⁷/VI in C Major:

Fig.1 V⁶/vi and V⁷/VI in C Major

Listen:

Here are the vii°⁶ and vii°⁷/ vi in C major.

Fig.2 vii°⁶/vi and vii°⁷/ vi in C major.

Listen:

The diminished vi° triad in the minor key is also unacceptable as a tonic chord

Fig.3 V/iii in C Major

Listen:

Fig.4 vii°⁶/iii and vii°⁷/iii in C Major

Listen:

Fig.5 V⁷/V leading to vii°⁷/iii

Listen:

Part III - Progressions and voice leading

I            iii              X/vi           vi           ii             V            I

and for the iii chord the progression is:

I            X/iii              iii           vi            ii           V             I

Remember that these two secondary dominants are rare in the minor keys.

Fig.6 secondary dominant sequence

Listen:

The sequence of secondary dominant progression follows the circle of fifths progression.  Be sure not to confuse this for a temporary key change.

I    X/iii             X/vi        V/ii              X/V           V         I