14b Lesson - Secondary Leading-tone Chords

Secondary leading-tone chords

Just as we can tonicize non-tonic chords by borrowing their dominant chords, we can also tonicize non-tonic chords by borrowing the leading-tone chord (vii^o) from that same key. A secondary leading-tone chord follows all of the same voice-leading rules as if it were written in the borrowed key.

There are two different ways to explore secondary leading-tone chords(vii^o/x)–through functional substitution as a dominant chord or through functional substitution as a pre-dominant chord.

Secondary leading-tone chords through functional substitution

In Unit 11b, we introduced the idea of functional substitution as a way to explore how chords with similar functions are related. To better understand the voice-leading of vii^o chords, I asked you to think of them as V⁷ chords without the root. This explains why vii^o breaks many of standard part-writing doubling conventions.

• You should not double the root, because it’s a tendency tone…like the third of the V⁷ chord.
• You should double the chordal third, because it is not a tendency tone…like the fifth of the V⁷ chord.

First, harmonize the following example as written, and then turn the ii⁷ chord into a V⁷/V by adding the appropriate accidental.

In doing this, you have created a well-voiced secondary dominant seventh chord, V⁷/V that should look something like this:

To turn this into a secondary leading-tone chord, you need to replace the root–in this case, the pitch D–with a note from vii^o/V. While this is a simple statement, I hope that you remember our discussions of the difficulties in voicing a vii^o triad. You do not want to double the tendency tones, because one of them will need to resolve incorrectly to avoid objectionable parallels with each other. And because there are so many tendency tones–the root, fifth, and seventh of any vii^o7 are all tendency tones–you need to be careful of where each voice is placed to avoid parallelisms, poor resolutions, and spacing errors.

As you work on revoicing your V⁷/V, take note of which pitch you choose to double. What other changes are necessary to avoid poor resolutions? You may choose to use any inversion for your vii^o/V chord, so try re-voicing using the following voicing:

Conclusions

If you tried to create your vii^o/V based on the V⁷/V voicing from above, it is likely that you immediately ran into issues in trying to eliminate the D from the bass. Substituting an A in the same octave creates parallel octaves against the tenor. If we do not alter our upper voices from the completed V⁷/V example, substituting an F-sharp in the bass creates parallel octaves against the alto. You could frustrate the leading tone in the alto as a workaround, but the fact remains: vii^o triads are difficult to use as a dominant function with good voice-leading, and there is no straightforward answer to the above exercise that does not result in some compromise.

Adding a seventh

It is much easier to use a vii^o as a seventh chord. In the following example, try to using a vii^o7/V using the provided bass line. You may use either a fully diminished or half-diminished seventh chord in this example.

Conclusion

As you can see, the part-writing mostly takes care of itself in voicing this chord as long as you resolve the tendency tones correctly. The most obvious solution is listed below. Notice that the resolutions are smooth and allow every tendency tone to resolve correctly without creating objectionable parallels.

Because this is a functional substitution for a V/V chord, the root and fifth of the vii^o7/V are acting as if they were the third and seventh of the V^6/5/V chord. You can see this when you voice the two chords side-by-side.

Secondary leading-tone chords through similar chords

It is also helpful to approach secondary leading-tone chords by exploring the dual nature of their function. To this point, we have focused on their role as dominant function chords in a second key. For example, we have shown repeatedly that a V⁷/V functions as the V chord in the key of V. This explains their voice-leading, but it does not address their actual function within the progression as a whole in the home key–the key of I. In the home key, the V⁷/V takes the place of a pre-dominant chord, most often replacing a ii chord, but like ii and IV, it can move laterally between them. (e.g. A ii7 can move to a V7/V and then resolve to V.)

This can be applied to vii^o7/x as well. Notice that the roots of both dominant function chords–V and vii^o–and the roots of pre-dominant chords–ii and IV–are separated by the interval of a third. If we add this observation to the idea that a V/V chord is a functional substitution for a ii chord, it reasons that a vii^o chord is therefore a functional substitution for a IV chord. They share a function and have a root that is a third higher than their more commonly used counterpart.

You can demonstrate this by harmonizing the following diatonic progression. Once you have a harmonization with good voice-leading, alter the IV⁶ chord to become the vii^o7 chord from the key of the chord you will be tonicizing–in this case, the vii^o7 from G major. What note(s) do you have to alter to achieve this? How do these notes relate to a V⁷/V? Did you have to re-voice this to accommodate the alterations?

After having done this, do you feel that vii^o is more closely related to ii⁷ or IV? Why?