Tonal harmony is easiest to study when when it follows strict rules, and because of this, we have studied harmonic function thus far through the lens of major and minor keys. In real music however, the relationship between modes is more fluid.
Look at the following chart of the chords of parallel major and minor keys. Compare the chords built off each diatonic scale degree. (e.g. I to i, ii to iio How many of these chords match qualities? Does this fit with your perception of two keys that are distantly-related?
| C major | Chord | Chord | C minor |
|---|---|---|---|
| I | C maj | C min | i |
| ii | D min | D dim | iio |
| iii | E min | E-flat maj | III |
| IV | F maj | F min | iv |
| V | G maj | G maj | V |
| vi | A min | A-flat maj | VI |
| viio | Bo | Bo | viio |
You will notice that the only common chords are the dominant function chords, and even these require alteration in minor to share function and qualities. So if we think about this as we did when discussing modulations, these keys should have little in common. On the other hand look at the following basic progressions in both keys. Do these look unrelated? How does the voice-leading differ between the two? How many chromatic pitches are required to make the second progression function?
Even at a glance, you can see that the voice-leading in these two progressions is identical with the only differences between the two resulting from the altered pitches in the key signature. In particular, the resolution from the sixth scale degree to the fifth scale degree is strengthened in minor, because the resolution becomes a half-step between le and sol.
When studying the voice-leading of these two parallel modes, they seem almost interchangeable.
And they are.
Alter the following progression in C major to “borrow” either the VI or iio chords from minor. What chordal members do you have to alter for each chord? What scale degrees are these? When you play it back does it sound acceptable? What if you only alter both chords? Does this make it more or less jarring?
To borrow either iio or VI from minor, you must alter the sixth scale degree for both, and the VI also requires an altered third scale degree. Regardless of which chord you alter–or both–the progression is fairly convincing. Borrowing from the minor mode greatly darkens the progression without changing any of the voice-leading functions. Also, take note of how the roots of chords are affected. The ii chord has a root of re in either the major or minor mode and changes only in quality from a D minor to a D diminished chord. The vi chord undergoes a more substantial change, because not only does its quality change from minor to major, but it does this by changing the actual root of the chord from la to le. Forgetting to alter the root when borrowing chords from different modes is one of the most common mistakes that students make when studying borrowed chords in mode mixture, so always check your roots before building the chord.
Perhaps more importantly than even understanding which chords can be borrowed, you must look at how they function. In this example, we are borrowing chords directly from a circle-of-fifths progression. They are still fulfilling their diatonic function, because the voice-leading is tendencies are the same regardless of mode. As with all Roman numeral analysis, its purpose is to explain the function and provide context for a progression. So even though the quality of this ii chord has changed and is no longer diatonic, the meaning of the Roman numeral doesn’t change unless you alter it with further information such as labeling it as a passing or pedal chord. If you put iio without further explanation, you are saying that it still has a pre-dominant function in this context.
The next progression is a longer example containing multiple cadences. Try borrowing each chord individually from the parallel minor. Which chords work and which don’t? Once you have an idea of which chords function best, try combining these into a single progression. How many chords can you borrow before it simply sounds as if its in minor?
Almost every chord can be substituted for its minor counterpart in this progression without changing its function. The pre-dominant and tonic functions can all be borrowed without altering their function, although altering the tonic functions quickly changes the sense of whether we are operating in the major or minor mode.
There are two chords that cannot be borrowed. The first is the minor v chord; if you borrow this, you undermine the fundamental core of diatonic tonality, so it sounds as if someone simply played a wrong note. The other non-borrowable chord for this progression is the major VII chord that would be built off of B-flat. Both of these chords demonstrate the importance of the resolution from the leading tone to the tonic to establish dominant and tonic function. This is the basis for tonal harmony.
Of note, you can borrow the viio7 from minor because it still has a leading tone.
The next example uses the same progression in minor. Alter one chord at a time to borrow it from the parallel major, and pay careful attention to which scale degrees you are altering. Which progressions sound acceptable to you? How does the voice-leading change when starting in minor? Pay careful attention to any enharmonically equivalent resolutions.
It is because of mode mixture that we have followed such strict guidelines when labeling Roman numerals to this point. By having each part of a Roman numeral describe an isolated chord tone, we are able to accurately describe even borrowed chords.
| Chordal member | Default implied pitch | To raise by semitone from default | To lower by semitone from default |
|---|---|---|---|
| root | diatonic scale degree | sharp symbol in front of Roman numeral* | flat symbol in front of Roman numeral* |
| third | based on case of Roman numeral | upper case (M3) | lower case (m3) |
| fifth | P5 above root | add + after Rom num | add o after Rom num |
| seventh | m7 above root | add M before inversion figure | add o before inversion figure** |
*For clarity’s sake, we always use a sharp or flat symbol to show that we are raising or lowering the root, even if you are actually adding a natural.
**Because the diminished o implies the interval of a d5 AND a d7, you must use the half-diminished symbol if you wish to alter the fifth but leave the chordal seventh as a m7 above the root.
Test your knowledge of this by writing the correct borrowed chords for every diatonic chord in a parallel major and minor. You may use the following chart as a model. With all of these make sure that you build the chord off of the correct root. For example, students often forget that to build a major VI chord in major, the root is altered thereby changing the entire chord. (In C major for example, the borrowed bVI chord is not an A major triad.)
| Roman numeral in major | Borrowed from parallel minor | Roman numeral in minor | Borrowed from parallel major |
|---|---|---|---|
| I | i | ||
| ii | iio | ||
| iii | III | ||
| IV | iv | ||
| V | V | ||
| vi | VI | ||
| viio | viio |
As you discovered above, certain chords do not sound good – or function at all – when borrowed. Because of this, there are a few chords that are borrowed most often.
Because of voice-leading resolutions, it is easiest to borrow chords while in major. The most commonly borrowed chords in major are:
Minor is more limited due to voice-leading limitations, but the following chords are commonly borrowed: