What Is a Chord? Three Notes Meet and Become a Color

In Part 1 we saw where the notes come from, and in Part 2 we met the distance between two of them (the interval). Now one step further — we press several notes at once. If a melody is a line traced one note at a time, a chord is a color made by layering notes together. This post builds up how a chord is made, and why some chords sound bright while others sound dark or uneasy.

Why stack notes on top of each other?

A melody is a single line flowing through time. But what happens when you sound two or three notes at the same time? The overtones we met in Part 1 blend together and a new sound is born — one a single note can't make on its own. We call it harmony. The same "do" feels restful or tense depending on what you stack with it, and that stacked-up bundle is a chord.

Why stack in thirds?

Building a chord is surprisingly regular. Pick a home note (the root), skip one step and add the note a third above, then skip again and add another. Starting on do, you get do-mi-sol.

Why thirds, of all intervals? Stack the note right next door (a second) and, as we saw in Part 2, the two notes cram together and clash. A third, on the other hand, is a consonant interval that blends cleanly, so layering them stays clear rather than muddy. That's why we build by skipping every other note. A three-note chord made this way is a triad, and its notes are the root, third and fifth from bottom to top.

Bright chords and dark chords

Here the "bright/dark switch" from Part 2 returns. Take do-mi-sol and lower just the middle note, mi, by a semitone (do–mi♭–sol). The chord that was beaming a second ago suddenly turns downcast.

So when the gap from the root to the middle note is a major third, you get a bright major chord; when it's a minor third, a dark minor chord. The top note (the fifth) stays put — that one semitone in the middle flips the whole mood. The note that decides a chord's expression is always the third.

The color of tension — diminished and augmented

Touch the top note too and stranger colors appear. Lower the fifth by a semitone and you get two minor thirds stacked — a diminished triad, jittery and anxious, the sound of a horror scene. Raise the fifth by a semitone and you get two major thirds stacked — an augmented triad, dreamy and unmoored, settling nowhere.

So major, minor, diminished and augmented are the four basic colors of the triad. One listen beats a hundred readings, so hear the four side by side and feel how their expressions differ.

How to read chord symbols

Those C, Am, G labels you meet on lead sheets are really shorthand recipes for "stack these notes this way." A capital letter is the root's name (C=do, D=re, E=mi, F=fa, G=sol, A=la, B=ti), and with nothing after it, the chord is major. A small m means minor (Am = A minor); dim and aug mean diminished and augmented. A number like C7 means an extra note stacked on top — that's a story for another day. Just being able to read these symbols lets you play the accompaniment on most sheet music.

Hear it — same melody, different chords

There's a perfect way to prove a chord really is a "color": keep the exact same melody and change only the chords underneath it. The same tune turns bright, then wistful, then jazzy and refined. Hear how the melody stays put while the chords swap its whole mood.

A single chord is one patch of color. But what happens when you line those colors up in order? The still image starts to move and becomes a story. In Part 4 we'll follow chords as they leave home and come back — chord progressions. If you haven't yet read the notes-and-intervals chapters, start with Part 1 and Part 2.