Leading-Tone Seventh Chords

Let's begin by reviewing the most frequent seventh chord constructed above scale degree 7, the V⁶₅. The chord progressions below should be very familiar:

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Operation 1

Exchanging scale degree 6 for 5 yields new harmonic possibilities.

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This half-diminished seventh chord occassionally appears in major mode, usually in root position.

Operation 2

The principle of mixture makes possible the following non-diatonic variants:

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The FULL-diminished seventh chord occurs VERY frequently in both major and minor modes and is an important new harmonic resource.

Note that the root position leading-tone seventh chord is fully diminished and contains TWO dissonant elements above the bass: a diminished 7th and a diminished fifth. Resolving both dissonant elements results in a root position tonic chord. This characterisitic voice leading will help us determine how leading-tone 7th chords function in inversion.

The resultant half-diminished and fully diminished seventh chords produced by operations 1 and 2 are called leading-tone seventh chords. Although these chords all sound different, their voice leading characteristics are quite similar. As the next example shows how leading-tone 7th chords function very much like linear dominant chords.

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In fact, the first three positions (root position, first, and second inversions) differ by only one note to their corresponding inversions of V⁷

vii^o7=V⁶₅
vii^o6₅=V⁴₃
vii^o4₃=V⁴₂.

vii^o7 (V⁶₅) as lower neighbor to I

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vii^o6₅ (V⁴₃) passing between I and I⁶

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Listen. vii^o4₃=V⁴₂ as upper neighbor resolving to I^{6

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Only the vii^o4₂(see below) does not correspond to any inversion of V⁷. Knowing, however, that this chord almost always resolves to V64 , can you explain its harmonic function?

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Keep Track of Your Resolutions!

The dim. 7 must resolve to a perfect 5th. In inversion, the aug. 2 resolves to a perfect 4th (i.e., ti-do and le-sol).
Try to resolve tritones in accordance with their spelling. This will result in a tonic with doubled 3rd.

Acceptable Irregular Resolutions

Sometimes the augmented 4th (vii^o4₂) resolves irregularly when scale degree 2 leads to 1 in the melody (i.e., instead of scale degree 3).
The diminished 5th may resolve to a perfect fifth with parallel 10ths in the outer voices
(just as in the progressions I-vii⁶-I⁶ and I-V⁴₃-I⁶).}