1. The Leading-tone Seventh Chord
Chapter 12
The Leading-tone Seventh Chord

2. vii°7
Very closely related to the V7 chord because both chords have three tones in common
Built on the seventh scale degree of the major, harmonic minor, and ascending melodic minor scales

3. vii°7 In major keys, the quality is half-diminished (dm)
In minor keys, the quality is fully diminished (dd)

4. Progression of the vii°7
Can be substituted for the V7 to add variety
Usually resolve to the tonic, or to the tonic through the V7

5. Resolution of the vii°7
The fully diminished seventh chord contains two diminished fifths, which are best to resolve inward. If resolved correctly, the result will be a doubled third factor in the tonic chord, but you can also use normal doubling.
The root of the vii°7 will resolve upward to the tonic, and the seventh factor will resolve down by a step

6. Pitfalls to avoid
Avoid parallel fifths between the third and seventh factors in the half-diminished seventh chord
Double the third factor of the tonic triad to avoid these parallels.
Parallel unequal fifths are permitted

7. Summary
Resolve the seventh factor of the vii°7 down one diatonic scale degree to the fifth factor of the tonic triad
Resolve the root upward to the tonic
The other two voices resolve to the third factor of the tonic triad