Reharmonisation Part 9: Modal Interchanges

Today, we're gonna talk about a harmonic approach that is probably the most "film music" sounding harmonic strategy and after we touched on it briefly in the last part of this series, let's have a closer look at this principle in more detail today.

I'm talking about modal interchanges. I'm pretty sure that most of you are aware of the fundamental concept behind that strategy but for everybody who is not, let's briefly explain it.

A modal interchange basically means to borrow notes from a scale with the same fundamental as the one you're currently at. So for instances, if you are writing a piece in C major, you can borrow notes from C minor, or C lydian and then switch back to your pitch material from C major. This can be done on a melodic level (which is the more common definition of Modal Interchange), so your melody uses pitches from another mode or on a harmonic level (which we want to talk about today) so you borrow chords from another mode.

Let's for instance have a look at the chords that we get out of C major and C minor:

In a nutshell, through modal interchanges we can relatively freely borrow chords from "the other side" into a chord progression. Most commonly we see chords from minor borrowed into a major chord progression and also constantly switching between these worlds is not a big deal. Let's have a look at just a few relatively common chord progressions that use this principle:

https://soundcloud.com/robin-hoffmann/modal-interchange-examples/s-5za6tjjDJij

So far so good. I think the principle is relatively clear and it creates this instant "film music" vibe. The great thing with this is that you can relatively easily expand your musical material and create unexpected colours so again, a very simple strategy has a very strong impact.

But as always, there's more to it. Firstly, this principle works with ANY mode, not just minor. Admittedly, borrowing between major and minor is the most simple way to apply this principle but if we stay at C, you could also borrow from any other mode of C, like lydian, phrygian or even more obscure scales.

Here's a cadence that is also very common in film music and borrows between lydian, major and minor:

This chord progression has been floating around a lot in film scores but I think the most iconic version of it is the Evey Reborn Sequence in V FOR VENDETTA where we hear it in Bbm.

But looking at the sequence, it starts out in minor, borrows next from lydian, going back to minor and borrowing the fourth chord from major before cycling back to the minor first chord.

Now with the realisation that every chord from every scale with the root note C could be used in a cadence in C (minor/major/etc.) in its fullest extend means that we can use every chord as you can either find or synthesize a scale of C that includes any chord that you are looking for.

So in spite of theoretically "anything goes", there are just a few actual chords that work well as modal interchange. E.g. the chords from minor are relatively "universally" in use, but you hardly would borrow something from C locrian that feels like its working well. That doesn't mean that it isn't possible but it is hard to sell.

It is a common misconception that harmonic modal interchanges force the melody to follow along into the interchange, meaning that if you borrow a chord from minor, your melody should move to minor as well for that chord. While this theoretically is true, there are common tones between major and minor which you could use and which allow harmonic modal interchanges on "plain" diatonic melodies.

For instance let's take this simple diatonic melody:

https://soundcloud.com/robin-hoffmann/part9-cue/s-UxxNkEhifgc

As this melody circles around scale degrees 1,2, 4 and 5 which are identical in major and minor, this opens up possibilities for many different modal interchanges in major as well in minor:

https://soundcloud.com/robin-hoffmann/modal-interchange-variants/s-6L2A5vJ8zTV

These are just a few (relatively random and partially not super successful) ones out of many more that are theoretically possible that simply switch back and forth between major and minor. You see that by using 7th chords or extensions, the possibilities get even greater and by using alternative bass notes other than the roots, even more options are possible.

The possibility to use these strategies on strictly diatonic melodies makes them also a great tool for reharmonisation. It can be a great new colour to have a main theme with a diatonic harmonisation and then later on in a further stage of development present it with one or several well picked modal interchanges.

These strategies are my bread and butter approaches as soon as I need something that is supposed to sound "filmic". They are again one of these tools that make things more interesting while remaining very digestible. There is nothing in these progressions where a general audience would not be able to follow along.

With all the quite simple approaches that we discussed in the previous nine parts, you can get a lot of mileage regarding harmonic diversity and interest. It is basically possible to cover 90% of the ground in film music with these harmonic approaches. For the remaining 10%, we will start to cover more advanced techniques in the following parts.