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Part-writing Inverted Chords: Mediant, Submediant & Leading Tone Triads

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This is the third of a series of Hubs describing the characteristics, patterns and part-writing usage for triads in first inversion. If you've missed the first two in the series, you can catch up using the links in the sidebar below.

Or perhaps you really haven't delved into part-writing before. In that case, starting a bit earlier in the sequence is almost surely a good idea. Or you may just come to feel, as you proceed, that this Hub is a bit too advanced for your current knowledge.

In cases such as those, you can use the sidebar, too--it contains a link to a summary Hub describing the content and suggested sequence of the preceding series. You can use it to access discussion and practice exercises on part-writing any root position triad. (As a convenience, it also lays out the 'rules' for part-writing, which are presented in a progressive manner throughout the first series of part-writing Hubs.)

Use it to pick a more compatible starting point, or just to make a quick self-placement check, or as a review tool!

Zambian violinist "Caitlin" plays inverted; we don't know about her chords.

Zambian violinist "Caitlin" plays inverted; we don't know about her chords.

In this Hub, we'll consider the first inversions of the triads built upon the 3rd, 6th and 7th scale degrees--the iii (III), vi (VI) and viio triads. First, the vi triad in its context in the major scale:

part-writing-inverted-chords-mediant-submediant-leading-tone-triads

Now a typical voicing of this triad:

Ex 2

Ex 2

Note that the third, C, is present in both soprano and bass. This 'doubling' of the third is normal for any secondary triad--the third of a secondary triad, after all, will be the primary tone present in the triad.

(The leading tone triad is a slight exception; in its case the fifth is the primary tone, but the third is still the usual tone to double. But that third is scale degree 2, which is also a strong and stable scale degree. One could jokingly call it an "honorary primary tone.")

One possible use of the first inversion submediant is to connect tonic and supertonic. As we've seen previously, the tonic-supertonic connection (like the subdominant-to-dominant connection) involves root motion by second, and this can be prone to creating objectionable parallel perfect intervals.

One way of connecting them is via an intermediary vi6, as shown in the example below.

Ex 3

Ex 3

VEx1

The possible parallel fifth between soprano and bass (beats 1 and 3) is avoided by moving the soprano first, creating the vi6, then by moving the other voices into the ii triad. (Note that there still could easily have been parallel octaves--they are avoided in this example by the tenor's contrary skip downward to the A.)

Compare a couple of other possibilities in harmonizing the same soprano:

Exa 4 & 4a

Exa 4 & 4a

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