Introduction
In the previous lesson on Secondary Dominants I distinguished between:
- Modulation = Changing key for a long period of time; and
- Tonicization = Changing key for a short period of time by using a dominant chord
It’s useful to make a similar differentiation between Modulation and Modal Interchange:
- Modulation = Changing key for a long period of time
- Modal Interchange = Changing key (using chords from a different key) for a short period of time while retaining the same ‘tonal centre’ (root note)
What ‘a long period of time’ compared to ‘a short period of time’ means is subjective.
Modal Interchange is used to add ‘colour’ to a chord progression and make it a little more interesting.
Relative vs Parallel Keys
It’s also worth quickly explaining the difference between a relative key and a parallel key:
- Relative key = two keys that have the same notes but a different root note (C Major & A natural minor)
- Parallel key = two keys that have different notes but the same root note (C Major & C natural minor)
In Modal Interchange you ‘borrow’ a chord from a parallel key. This is why using ‘Modal Interchange’ is also called using ‘Borrowed Chords’. You can ‘borrow’ a chord from a parallel key or mode, and as long as the chord progression is still leading towards the ultimate tonic chord, it won’t sound like you’ve completely changed key – it won’t be ‘Modulation’.
Modal Interchange & Borrowed Chords
Below is a table of all the Modes of the Major Scale, the Melodic Minor Scale and the Harmonic Minor scale and all their associated chords – both in Roman Numerals and from the root note of C.
Roman Numbers
| Scale | 1 (Root) | 2 | 3 | 4 | 5 | 6 | 7 |
|---|---|---|---|---|---|---|---|
| Ionian | IMaj7 | IIm7 | IIIm7 | IVMaj7 | V7 | VIm7 | VIIm7♭5 |
| Dorian | Im7 | IIm7 | ♭IIIMaj7 | IV7 | Vm7 | VIm7♭5 | ♭VIIMaj7 |
| Phrygian | Im7 | ♭IIMaj7 | ♭III7 | IVm7 | Vm7♭5 | ♭VIMaj7 | ♭VIIm7 |
| Lydian | IMaj7 | II7 | IIIm7 | #IVm7♭5 | VMaj7 | VIm7 | VIIm7 |
| Mixolydian | I7 | IIm7 | IIIm7♭5 | IVMaj7 | Vm7 | VIm7 | ♭VIIMaj7 |
| Aeolian | Im7 | IIm7♭5 | ♭IIIMaj7 | IVm7 | Vm7 | ♭VIMaj7 | ♭VII7 |
| Locrian | Im7♭5 | ♭IIMaj7 | ♭IIIm7 | IVm7 | ♭VMaj7 | ♭VI7 | ♭VIIm7 |
| Melodic Minor | ImMaj7 | IIm7 | ♭IIIMaj7#5 | IV7 | V7 | VIm7♭5 | VIIm7♭5 |
| Harmonic Minor | ImMaj7 | IIm7♭5 | ♭IIIMaj7#5 | IVm7 | V7♭9 | ♭VIMaj7 | VIIo7 |
Root C
| Scale | 1 (Root) | 2 | 3 | 4 | 5 | 6 | 7 |
|---|---|---|---|---|---|---|---|
| C Ionian (C Major) | CMaj7 | Dm7 | Em7 | FMaj7 | G7 | Am7 | Bm7♭5 |
| C Dorian (B♭ Major) | Cm7 | Dm7 | E♭Maj7 | F7 | Gm7 | Am7♭5 | B♭Maj7 |
| C Phrygian (A♭ Major) | Cm7 | D♭Maj7 | E♭7 | Fm7 | Gm7♭5 | A♭Maj7 | B♭m7 |
| C Lydian (G Major) | CMaj7 | D7 | Em7 | F#m7♭5 | GMaj7 | Am7 | Bm7 |
| C Mixolydian (F Major) | C7 | Dm7 | Em7♭5 | FMaj7 | Gm7 | Am7 | B♭Maj7 |
| C Aeolian (E♭ Major) | Cm7 | Dm7♭5 | E♭Maj7 | Fm7 | Gm7 | A♭Maj7 | B♭7 |
| C Locrian (D♭ Major) | Cm7♭5 | D♭Maj7 | E♭m7 | Fm7 | G♭Maj7 | A♭7 | B♭m7 |
| C Melodic Minor | CmMaj7 | Dm7 | E♭Maj7#5 | F7 | G7 | Am7♭5 | Bm7♭5 |
| C Harmonic Minor | CmMaj7 | Dm7♭5 | E♭Maj7#5 | Fm7 | G7♭9 | A♭Maj7 | Bo7 |
Notice that all the scales have the same root note – C – so they are all ‘parallel’. This means you can borrow any chord from any of these ‘keys’.
So let’s take a II-V-I in the key of C Major and borrow some II-V’s from different modes:
| Major | Dm7 | G7 | CMaj7 |
|---|---|---|---|
| Harmonic Minor | Dm7♭5 | G7♭9 | CMaj7 |
| Aeolian | Dm7♭5 | Gm7 | CMaj7 |
| Phrygian | D♭Maj7 | Gm7♭5 | CMaj7 |
| Lydian | D7 | GMaj7 | CMaj7 |
We can ‘borrow’ the II-V chords from any of the other ‘parallel keys’. All of these are plausible ‘modal interchanges’, because the tonal centre stays the same – C. The chord progressions still feel like they are leading towards the CMaj7 chord.
However, some ‘borrowed chords’ work better than others and thus are used more often than others. Remember the definition of ‘modal interchange’ is a change of key while still retaining the same tonal centre. The Lydian mode ‘modal interchange’ has a D7 moving to the GMaj7. This creates a V-I perfect cadence which makes it sound like the tonal centre is G (that’s the nature of a V-I cadence – that’s how tonicization works). But we want C to sound like the tonal centre, so this particular modal interchange doesn’t work very well.
The Harmonic Minor II-V ‘modal interchange’, on the other hand, works very well as it still retains the C as the tonal centre because of that altered G7 chord.
By far, the most common borrowed chords you will come across are between the Major Scale and a parallel minor scale. Some especially common borrowed chords are:
| Mode | Modal Interchange | Songs |
|---|---|---|
| Aeolian | - Minor iv - ♭VII7 (Backdoor progression) - ♭VI - ♭III | - All The Things You Are - I Got Rhythm - There will never be another you - My Romance - Lament - Lady Bird - Misty - Cherokee |
| Harmonic Minor | - Minor II-V | - Alone Together - What is this thing called love? - You Go To My Head |
| Mixolydian | - I7 | - Every Blues Song - I Got Rhythm - Alone Together |
If we look at Section A of I Got Rhythm, we see the below chords.
| I Got Rhythm | |||
|---|---|---|---|
| B♭6 - Gm7 | Cm7 - F7 | B♭6 - Gm7 | Cm7 - F7 |
| B♭6 - B♭7 | E♭6 - E♭m7 | B♭6 - Gm7 | Cm7 - F7 |
The Red chord are borrowed from the Mixolydian and Aeolian modes.
| Mode | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
|---|---|---|---|---|---|---|---|
| B♭ Major | B♭Maj7 | Cm7 | Dm7 | E♭Maj7 | F7 | Gm7 | Am7♭5 |
| B♭ Mixolydian (E♭ Major) | B♭7 | Cm7 | Dm7♭5 | E♭Maj7 | Fm7 | Bm7 | A♭Maj7 |
| B♭ Aeolian (D♭ Major) | B♭m7 | Cm7♭5 | D♭Maj7 | E♭m7 | Fm7 | G♭Maj7 | A♭7 |
Notice that:
- The borrowed chords are surrounded on both sides by chords from the key of B♭ Major
- The ‘key change’ only happens for ½ a bar
- The ‘tonal centre’ still sounds like it is B♭
Therefore, this is NOT modulation but rather modal interchange.
But this raises the obvious question, how long does a modal interchange have to be before it becomes a modulation? Obviously, there’s no answer to this question. It’s subjective, because the answer depends on what you perceive the tonal centre or root note to be. If you hear a change in the tonal centre – then it’s modulation. If you do NOT hear a change in the tonal centre – then it’s modal interchange. And so the line between modulation, toniciziation and borrowed chords, is fuzzy.
Also notice that you can borrow the same chord from a number of different modes. For example, you can borrow the ‘Fm7’ from the Phrygian, Aeolian, Locrian, and Harmonic minor scales. Now, an Fm7 is an Fm7, so it doesn’t really matter which mode you ‘borrowed’ it from – but the answer will depend on the analysis of the whole chord progression.
Theoretical Convergence
As I mentioned in previous lessons, there are many ways of analysing the same chord progression each of which is correct. Take, for example, the song How High The Moon (in the key of G Major). There is a section of that song that goes as follows:
What is the circled B♭7 chord?
- A passing chord to Am7?
- A tritone substitute for a secondary dominant to Am7?
- A borrowed♭III7 chord from Phrygian Mode (Modal Interchange)?
All of these are plausible explanations for this single chord.
And if modal interchange is just borrowing a chord from a parallel key, then there’s no reason you need to limit yourself to the modes of the Major Scale or the Melodic or Harmonic minor. You could also use chords from the modes of the harmonic minor or melodic minor or from the diminished or augmented or wholetone scales. You can use chords derived from any scale that has a root note of C.
For example, Take the A Train is in the key of C Major and uses a:
- D7#11 – which is derived from the Lydian Augmented Scale (which is the 4th mode of the melodic minor scale); or
- D7♭5 – which is derived from the wholetone scale.
So you can borrow any chord from any scale, as long as the root note (or ‘tonal centre’) stays the same.
In Practice
You will find borrowed chords in the chord progressions of many Jazz Standards. Keep an eye out for them. However, you can also add borrowed chords (just like passing chords) to make a chord progression more interesting. It’s up to you.