In the previous article, we said "a major chord = Root + 3rd + 5th." Remember? Play those three notes at the same time — that's a chord.
🎬 Why do songs have chords?
A melody is a single line — notes moving one after another. It's the star of the song.
But melody alone can feel a little "thin." Something's missing. Add multiple notes sounding together — a chord — and suddenly the melody gains an emotional backdrop.
Try this thought experiment:
Imagine a single note: middle C.* Play it over a C major chord (C–E–G) → it sounds bright and settled
* Play it over an Am chord (A–C–E) → the same C now sounds wistful
Same melody note. Only the chord changed. Yet the emotion is completely different.
A chord is the emotional backdrop that tells the melody "here's how to feel right now."
Think of it like a movie: the dialogue is the melody; the lighting and score are the chords. Same line, different lighting, totally different scene. Chords work exactly that way.
That's why songs have chords. They supply the emotional "color" that melody alone can't convey.
🎯 Just remember these 3 things
① A chord is notes stacked using intervals (Root + 3rd + 5th)
② The type of 3rd decides "bright" vs "dark" (Major vs Minor)
③ Line up chords and you get a "chord progression" — the flow of a song
Nail these three, and you'll see how chords work from the inside out.
🎨 ① Chords are intervals stacked together
Building a chord is simple: stack notes using intervals.
The smallest unit is Root (1st) + 3rd + 5th — three notes. This is called a triad.
5th (G) ─┐3rd (E) ─┤ ← Stack 3 notes = triad
1st (C) ─┘
The intervals you learned in Article 2 apply directly. Set the root to C and you get C–E–G; set it to G and you get G–B–D. Same interval pattern, any root.
🌈 ② The 3rd decides bright vs dark
The single most important note in a chord is the 3rd.
| Type | Degrees | In C | Character |
|---|---|---|---|
| Major | 1 – 3 – 5 | C – E – G | Bright, stable |
| Minor | 1 – ♭3 – 5 | C – E♭ – G | Moody, introspective |
The only difference is the 3rd. Lower it by a half step (♭3) and the chord turns minor.
A single half step flips bright to bittersweet. The 3rd is the note that sets a chord's "color."
That's also why the C note sounded different at the start of this article — the 3rd in C major (E) vs the 3rd in Am (C) changed the emotional context around the same melody.
Two more triad types
Master major and minor first. Think of these two as special "tints" to learn by ear:
| Type | Degrees | In C | Character |
|---|---|---|---|
| Diminished | 1 – ♭3 – ♭5 | C – E♭ – G♭ | Tense, unstable |
| Augmented | 1 – 3 – ♯5 | C – E – G♯ | Floating, pushing forward |
🔮 Add one more note: seventh chords
Stack a 7th on top of a triad and you get a seventh chord (four-note chord).
Start with these three:
| Name | Degrees | In C | Character |
|---|---|---|---|
| Major seventh (M7) | 1 – 3 – 5 – 7 | C – E – G – B | Smooth, melting; ballads & city pop |
| Dominant seventh (7) | 1 – 3 – 5 – ♭7 | C – E – G – B♭ | Gritty, pushes forward; blues |
| Minor seventh (m7) | 1 – ♭3 – 5 – ♭7 | C – E♭ – G – B♭ | Smoky, settled; R&B & soul |
Roles of the 3rd and 7th
* 3rd → bright or dark (major vs minor) = the chord's "color"
* 7th → rest or go = the chord's "direction"
A dominant 7 with its ♭7 has an especially strong pull — it wants to move to the next chord. We'll explore this "pull" more in the diatonic article.
🔗 ③ Line up chords and you get a "progression"
One chord sets a mood. A sequence makes the music move. That sequence is a chord progression.
Some famous examples:
* C → Am → F → G — The classic; balances comfort and longing
* Dm → G → C — Jazz staple II–V–I; add 7ths and the pull becomes obvious
* E → A → B → E — Rock conviction; works even as power chords
Why these chords feel right in this order connects to keys and diatonic harmony — we'll get there soon.
A chord progression is the blueprint for a song's story. Starting next article, we'll learn how that blueprint works.
🎛️ Experience chords in OtoTheory
OtoTheory lets you hear theory in action:
* Chord Progression Builder: Tap chord cards to build progressions. Compare major ↔ minor and M7 / 7 / m7 on the spot. Swap chords while playback runs — DJ-style — and hear how order changes feel
Find Chords: Pick a key and scale, and see every available chord with interval degrees. Instantly understand why* each note belongs* Fretboard display: On guitar, bass, or keyboard, chord tones light up in real time as the progression plays. See exactly where the root, 3rd, and 5th sit
✅ Recap — just remember these 3 things
① A chord is notes stacked using intervals (Root + 3rd + 5th = triad)
② The type of 3rd decides "bright" vs "dark" (Major vs Minor)
③ Line up chords and you get a "chord progression" — the flow of a song
* Triads: master major / minor first
* Seventh chords: M7 / 7 / m7 are the core three
* 3rd = "color," 7th = "direction"
Frequently asked questions
Do I need to understand intervals to learn chords?You can memorize chord shapes by rote, but learning them by interval lets you pick up many chords at once. A major chord is always root, 3rd, 5th, so learn that one formula and you effectively know all 12 major chords (a minor chord is root, ♭3rd, 5th). If intervals are still fuzzy, reading Intervals first will speed things up.
Can I play chords without reading sheet music?Absolutely. A chord is really just a pattern of stacked notes, not something you read off a page, so you don't need to read music. OtoTheory also shows each chord's notes and intervals on screen.
How do I tell major and minor chords apart by ear?You can judge it intuitively by whether it sounds bright or dark, but the difference comes down to the 3rd. A major 3rd makes it major; lower it a half step to a ♭3rd (minor 3rd) and it becomes minor. Instead of stopping at "sounds dark, must be minor," tying it to the theory — "that's a ♭3, which is why it sounds dark" — sharpens your ear over time.
There are so many chord types — how many do I need to memorize?You don't need to memorize them all. Start with the basic major and minor triads, then add maj7, 7, and m7. Those alone cover a huge range of songs.
Should I learn chords on guitar or piano?Either works. The underlying logic — stacking notes by interval — is the same whatever the instrument. OtoTheory can show a chord's notes on guitar, bass, and keyboard alike.
Next, we'll learn which chords belong to which key — the "home ground" of a song.
It's the first step to understanding why certain chord orders feel so good.