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As a kid, I knew chords were a lot of notes played at once. And I thought I knew why we had them: Melodies sound too plain by themselves, so we add chords to kind of fill it in, like the background of a painting.

I got better. The relationship between melody and chords (harmony) is much more interesting. We follow the melody like a hero. Behind and around the hero, the harmony provides an unfolding emotional story. It can be a simple home/away/home again story, or more of a leave home, get hit by bus, go to hospital, fall through trapdoor into your own bedroom and discover it was a dream kind of story.

The harmony is not just scenery — it’s what is happening to the hero. To understand how that works, we’ve got to get into the weeds a bit. Bear with me — cool toys are coming, and you’ll need these tools to play with them.

Each basic chord (or triad) consists of three pitches, like words consist of letters. Chords in combination communicate emotion, just as words in combination communicate meaning.

Keys don’t consist of seven notes so much as seven chords (triads). To build those triads, start with the seven notes of the C major scale (plus C again on top):

Keys 2

Now stack pitches on top of them in thirds.

Reminder: From one pitch to the next in the scale is a second, so C to E is a third, as is D to F, E to G, F# to Ab, etc. Doesn’t matter if sharps or flats are involved — it might be a different kind of third (major, minor, augmented, diminished), but it’s still a third:


Start with a note, add a third above it, then add another third above that one. You end up with stacks of three notes on the lines, or three notes in the spaces, like so:

C Major scale chords

These are the building blocks of musical meaning. Now let me add some information:


If it feels like the first time you looked at a periodic table, steady on — this is easier than it looks. Like the periodic table, it packs in a huge amount of powerful information once you know how to look at it.

The three lines of symbols contain different information about the triads. The digits on top are the simple degrees of the scale itself — the bottom note of each triad, 1-2-3-4-5-6-7, which in C major is C-D-E-F-G-A-B.

The bottom line is what you see on guitar music. These show the pitch on which each triad is based (also called the root of the triad) and the form the triad takes. Uppercase is major, lowercase is minor, and “dim” is diminished (more on that eventually).

The line of Roman numerals is just a way of combining the other two. The Arabic digit (like 5) becomes a Roman numeral (V), and the case of the Roman indicates major or minor. (The little degree circle means diminished.)

We can do the same thing with any starting pitch, any scale. The A major scale has C, F, and G sharped (raised by a half step) to fit the whole-step/half-step pattern of the major scale:

A maj works

…and so on for any pitch, any scale. The chord symbols on the bottom change, but the Romans stay the same because the chords are fulfilling the same function in each key — the same “words” with a different home (I). I’ll be using the Romans a lot from now on to talk about what’s going on in the harmony of a piece. If I say the chords are I vi IV, it means you hear a major triad built on the first note of the scale, then a minor triad on the sixth note, then a major triad on the fourth note. But instead of 27 words, I use three symbols: I vi IV.

These three-note triads, much more so than the notes of the scale, are the emotional words of music, the bricks out of which everything is built.

One important point: In the actual music, the notes don’t have to be in that order. They can be exploded out in any order top to bottom. This just reduces it to what’s called simple position, with the notes in the closest possible intervals to figure out what chords they are. Kind of like putting all the letters of a word in alphabetical order, except in music the meaning doesn’t change.

These are all C major triads, for example:

All C Major triads

The composer might spread them out like that for different textures and effects. But if I want to figure out what’s going on in the harmony, I can put the last three in simple position with C on the bottom, and their harmonic identity becomes clear.

Okay, back to the triads of C major:


I remember being surprised to learn that a major key consists mostly of non-major chords. But it’s a good thing it does — that variety makes it work, giving you a road map so you know where you are relative to home. And your ear knows how to follow that map. Of course it does — you’ve passed this way ten thousands times before.

As the music moves along through time, left to right, it passes through different chords, and the sequence of chords makes us feel a certain emotional narrative. Same as language: These phrases start with the same three words, but the last three lead to very different places:

  • For sale: baby turtles, too cute!
  • For sale: baby shoes, never worn.

It works the same in music. Suppose you hear a major chord alone — let’s say it’s an F major triad:

Is that the tonic home? Dunno. It is if we’re in F major. But an F major chord could also be IV in the key of C. Can I get an amen, people:

Or V, the neon arrow, pointing to a Bb home:

In each case, before we could know what the F triad means, we needed another reference point. Once you have two chords, your ear starts to triangulate on home. Let’s say we hear two major triads next to each other, ascending — F major and G major:

When you look at the map for a major key, there’s only one place with two adjacent major chords, one place it fits in the aural landscape — IV to V.

And here’s the crazy great thing. You don’t need to see the map or know the Romans. When your ear hears an F major triad, then a G major triad, your ear instantly knows where home is. Sing it! You know where it’s going! Sing where it’s going, dammit!

C major is home.

So that’s a simple example of starting somewhere harmonically (F) and ending up at different homes (F, Bb, and C). That’s the tip of the tip of the iceberg. Composers use these ambiguities to mess with you, moment to moment, leading you to expect one direction and giving you another. It’s like those “garden path” sentences:

  • The old man the boat; the young watch from shore.
  • The man who hunts ducks out on weekends.
  • The cotton clothing is made of grows in Mississippi.
  • Mary gave the child the dog bit a Band-Aid.

Back to music for a while, including some unweaving that goes further into the harmony/hero relationship.

If you’re new here, or you want to review, you can start at the first post, or work your way through Just Enough Theory in the right sidebar. Quick and fun.

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Dale McGowan is the author of Parenting Beyond Belief, Raising Freethinkers, and Atheism for Dummies. He holds a BA in evolutionary anthropology and a PhD in music.