The last section showed how to find the scale degrees of a secondary chord by lining up two Hooktheory staffs to find the relationship of the chord in the original scale with the scale being used to construct the secondary chord. This section extends this technique to find the scale degrees of borrowed chords.
With secondary chords, the home bases of the two relevant scales are different. For example, for a V/vi chord, the original scale starts on scale degree 1, whereas the secondary scale starts on scale degree 6. When you want to borrow a chord, the situation is a bit different. In this case, you are in one mode and you are borrowing a chord from a parallel mode. This means that the home base of the two scales is the same, but the scales themselves are different.
For example, say you want to borrow a “six” chord from the minor mode into the major mode. To figure out the scale degree in this borrowed “six” chord, we need to compare the major scale (the home scale) with the minor scale (the borrowed scale). Start with the Hookpad staff showing the uncompressed major scale and put the uncompressed minor scale next to it with scale degree 1 of each scale next to each other, as shown below:
Notice that because the minor scale contains different notes, some of the scale degrees line up and others don’t. The “six” chord always contains scale degrees 6, 1, and 3. To determine the corresponding scale degrees of this chord, find scale degrees 6, 1, and 3 from the minor scale and look across to see what these scale degrees correspond to in the parallel major scale.
The scale degrees in the major scale are ♭6, 1, and ♭3. These scale degrees form a major chord (“six” chords built from the minor scale are always major in quality). The major chord built off scale degree ♭6 is a ♭VI chord. This technique can be used to find the scale degrees and chord name of any chord borrowed between any two modes.