Music Theory for the 21st-Century Classroom

Below are the secondary diminished chords that occur in major and minor.

Notice that ${\text{vii}}^{\circ }/\text{III}$ in minor is not included because it is ${\text{ii}}^{\circ }$. Notice also that ${\text{vii}}^{ø}{}^7/\text{III}$ has no accidentals—it is the same as ${\text{ii}}^{ø}{}^7$ but functions differently. The ${\text{ii}}^{ø}{}^7$ chord has pre–dominant function and progresses to $\text{V}$ whereas the ${\text{vii}}^{ø}{}^7/\text{III}$ chord progresses to $\text{III}$.

Minor triads are tonicized by fully diminished seventh chords. Major triads are traditionally tonicized by half diminished seventh chords but can also be tonicized by fully diminished seventh chords.