Music Theory for the 21st-Century Classroom

Borrowed chords, or chords making use of mode mixture, are handled similarly to their diatonic versions in terms of voice leading, e.g., ${\text{ii}}^{ø}{}^7$ is handled similarly to ${\text{ii}}^7$. In any of the borrowed chords with ♭$\hat{6}$, resolve this tendency tone down by step whenever possible.

Another situation where you may encounter a borrowed chord is the $\text{V}$–♭$\text{VI}$ cadence, which should be handled the same as the deceptive cadence in minor (see Principle 26.7.4)—resolve the 3rd of the $\text{V}$ chord up by step and move the other two voices in contrary motion to the bass.

There are no specific rules for other borrowed chords such as ♭$\text{III}$, ♭$\text{VII}$, $\text{i}$, and $\text{v}$; simply voice lead them as smoothly as possible while avoiding objectionable parallels.