Expanding our chord “colour pallet” with Modal Interchange.

One of the challenges when composing our music is to be creative, original, but at the same time keeping the consistency in our chords progressions. Modal Mixture, or Modal Interchange, can help us increase our Harmonic possibilities.

As composers, we already know we have seven Diatonic Chords that belong to each scale. In the major mode, we have seven different diatonic triads:

I, ii, iii, IV, V, vi, viib5

In C major scale, these chords are:

C, Dm, Em, F, G, Am, Bdim

With the addition of the seventh note:

Imaj7, ii7, iii7, IVmaj7, V7, vi7, vii-7b5

An example in key C major:

Cmaj7, Dm7, Em7, Fmajr7, G7, Am7, Bm(b5)

The major scale is just one of many Modes we can use. This scale is also called “Ionian”, one of the seven Greek modes which were used until Polyphony was developed during the Renaissance. In the Baroque period, all these Modes were not used as such but survived in subtle ways.

With modal interchange, also known as Modal Mixture, we can borrow chords from parallel modes to use them temporarily in our pieces or songs. This will widen our options on a harmonic level, as well as melodic, without jeopardising the stability function of our Tonic chord.

This technique is not new, it has been around from the Baroque period and is still pretty much alive in different genres, such as rock, pop and Jazz, that keep on using modal interchange chords. To quote a few, we have Radiohead, Thelonious Monk and Muse.

Differences between Parallel and Relative Tonality:

Before we start with Modal Mixture, we should see what constitutes a Parallel tonality and what a Relative one. Parallel tonalities or Modalities are scales that share the same tonic but different tones and semitones relation, for example, C major, C minor, C Dorian, C Phrygian, etc. Each one of these examples has different qualities but they all start on the C note.

Relative tonalities share the same notes but different tonic. For example, C major and A minor natural. We find relatives tonalities in the Greek modes, strongly related to Modal Mixture.

Let’s start from the easiest example, the modal interchange from major to a minor scale.

Here are all the diatonic chords that belong to the parallel key of C minor (remember: parallel key always starts from the same tonic chord/note that the key we are already in):

Cm7, Dm (5), Ebmaj7, Fm7, Gm7, Abmaj7, Bb7 (corresponding to the I, ii, III, iv, v, VI and VII of C minor mode)

The only chords we cannot borrow are the Cm7, which will have a counteractive impact on the stability of our major tonic, and Dm7 (b5) which has a strong pull towards Eb (this resolution will threaten the stability of our tonal center) The rest, can be safely used as replacement of, in most common cases, the subdominant chord family.

Here we have a progression in C major:

C – F – Em – Dm – G7 – C

Or, in Roman numerals:

I – IV – iii – ii – V7 – I

We can replace the IV, as well as the iii degrees with a modal interchange from the C Aeolian (or C natural minor) The example would be like this:

C – Fm – Eb – Dm – G7 – C

In this case, the subdominant chord, F is transformed into a minor and the third degree, before minor, now will bring another light converted into a flattened major. As we can see, the stability of the key chosen (C major) has not been affected as we have a perfect cadence by the ii – V7 – I afterwards.

We will see how we can use these chords in depth on the next article by using primary and secondary modal chords, and we will learn about the modal interchange chart too!

Learn how to use Modal Interchange.

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