A common musical pattern is the descending chromatic bass line ($\hat{1}$ –$\hat{7}$ –♭$\hat{7}$ –$\hat{6}$ –♭$\hat{6}$ –$\hat{5}$ ). Composers harmonize descending chromatic bass lines in different ways, sometimes with secondary chords, borrowed chords, and augmented sixth chords. Below are some examples from the past four centuries.
For the harmonization of scale degree $\hat{6}$ , remember that the concept of ♯$\left.\text{vi}^{\circ}{}\right.$ was introduced when Roman numerals in minor were introduced. The notes of the ♯$\left.\text{vi}^ø{}^{7}\right.$ chord belong to the melodic minor scale.