Practical Chord Progressions: iii (The Mediant or “Moody Chord”)

In this article, we’ll be exploring the power of the iii to shift the mood of our song. We’ll also be looking for the first time at the idea of musical phrases, questions, and answers. All of this in the form of a very simple exercise.

At this point, you’ve hopefully started to get a pretty solid grasp of the chords available in a single key. We have already:

  1. looked at the home chord (I), around which everything else takes on its meaning,
  2. looked at the magnet chord (V), which pulls us back toward home and reinforces its power,
  3. strengthened this sense of inevitability by building a magnetic tunnel moving from ii to V and finally to I, and
  4. explored other mini-centers in the neighboring IV and the more mysterious vi.

Today we are going to look at the last of the in-key chords that I’ll be discussing for the time being: the iii. This is a chord with the power to bring about sudden shifts in mood, and to glue together ascending and descending progressions (I-ii-iii-IV, iii-ii-I, V-IV-iii-ii, etc.).

[In case you’re wondering, the diminished vii is a bit trickier to use, so I’ll be leaving discussion of it until later in the series].

There are many ways to create an interesting song. One approach that is worth exploring is thinking of your creation in terms of the interplay of light and shadow, a point I will be exploring in more detail in the next couple of posts.

For the time being, I want you to focus on the interest created by the contrast between the major I and the minor iii. The move from I to iii creates a sudden shift in mood, but not a terribly disorienting one. We can immediately regain our sense of home by moving to the five, perhaps via the ii or the IV.

Let’s get to the exercise and see what this kind of thing sounds like.

As always, we’ll be approaching this exercise in the key of C major, though you are free to try it in other keys (and I encourage you to eventually do so, of course!). If you’re sticking with C major as the I, then your iii is E minor.

Begin as you have in the past by getting comfortable on the I.

Now move to the iii. Notice that shift in mood? Things have gotten a little darker and a lot more uncertain. That’s the power of harmonic shadows.

Ok, now I want you to move back and forth between these two chords, spending a measure or two on each. Come up with a melody to match this progression.

For the purposes of this exercise, try to either repeat the exact same melody for every I-iii you play, or use closely related melodies. What you’ve just created is a musical phrase. It’s going to serve as a kind of musical “question” which demands an answer.

Now try the following: play I-iii twice through while singing your melody. Then choose two other chords from the ones we’ve discussed and move to those, singing a musical “answer” over them. Don’t worry too much about what “answer” means; just come up with whatever sounds right to you.

Now return to the I-iii, playing it once without singing.

Repeat. I-iii-I-iii-?-?-I-iii

So what chords should you use to fill in the blanks? I recommend trying a variety of combinations, but a simple starting place is ii-V, since you know that will get you back to I in a satisfying way. But don’t limit yourself. See what else is possible!

Here’s a more detailed map: [Question: I-iii]-[Question: I-iii]-[Answer: ?-?]-[No singing or an end to your answer: I-iii]

Once you’ve come up with something you like, submit it to the site to help give us a sense of how many phrases one can create over the same two chords, as well as how many kinds of contrast one can build using only two more.


  1. Play I-iii while singing a melody.
  2. Repeat I-iii with the same or a very similar melody. This is your musical question.
  3. Play two more chords, choosing from ii, IV, V, and vi. Sing a new melody over these chords. This is your musical answer.
  4. Play I-iii again either without singing or while singing an extension of your answer from 3.
  5. Repeat!

Next: Light and Shadow Part 1 – Verse and Chorus

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John Thomas Mumm has been writing and studying music since 1997. He has recorded hundreds of songs and five self-produced albums. His day job is as an academic philosopher, and in his spare time he writes fiction and brews beer. Most recently, he's started studying the fine art of the cocktail. So far he's finding that the principles of balance in drink mixing aren't completely unrelated to the principles of balance in songwriting.

One thought on “Practical Chord Progressions: iii (The Mediant or “Moody Chord”)”

  1. C – Em – Dm – G

    I noticed after I came up with it that it was already used in that Beatles song “Girl.”

    I just wanted to post this because your lesson helped a lot.. Thank you.

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