Section 17.3 Secondary Dominants in Major and Minor
Both major triads and major–minor seventh chords can be secondary dominant chords.
Notice the chromaticisms in the example above. The raised notes generally act as the leading–tone to the root of the chord being tonicized. In the major mode, the only secondary dominant with a lowered chromaticism is \(\left.\text{V}^{7}\middle/\text{IV}\right.\). The lowered note in \(\left.\text{V}^{7}\middle/\text{IV}\right.\) acts as \(\hat{4} \) of the chord being tonicized in the same way the last flat of a key signature is \(\hat{4} \).
Below are all secondary dominant chords (triads and major-minor seventh chords) in the minor mode.
Remember that both \(\left.\text{vii}^{\circ}{}\right.\) (on raised \(\hat{7} \)) and the subtonic \(\left.\text{VII}\right.\) (on the lowered \(\hat{7} \)) (see Definition 7.3.2) occur in the minor mode. The subtonic \(\left.\text{VII}\right.\) can be tonicized with \(\left.\text{V}^{7}\middle/\text{VII}\right.\), while \(\left.\text{vii}^{\circ}{}\right.\), being diminished, cannot.
Notice that an F major chord in C minor can be \(\left.\text{V}\middle/\text{VII}\right.\) or \(\left.\text{IV}\right.\), depending on how it functions or progresses. If the F major chord progresses to a B♭ chord, label the F chord as \(\left.\text{V}\middle/\text{VII}\right.\). If the F major chord has pre–dominant function and progresses to a G major chord (in any inversion) or \(\left.\text{B}^{\circ}{}\right.\), label the F chord as \(\left.\text{IV}\right.\).
The \(\left.\text{B}^♭{}^{7}\right.\) chord, on the other hand, can be labeled correctly as \(\left.\text{V}^{7}\middle/\text{III}\right.\) or \(\left.\text{VII}^{7}\right.\) because both \(\left.\text{V}^{7}\middle/\text{III}\right.\) or \(\left.\text{VII}^{7}\right.\) progress to \(\left.\text{III}\right.\) in minor.
