Chords

Here's a C major chord, rolled from the bottom up the way a guitarist or harpist might play it. It sounds open and settled, like a sunny room.

Now lower just the E by one semitone. Four of the five notes didn't move, and the light in the room went out. That's C minor. If you took the G away entirely and kept only C and the changed note, would you still hear the difference between major and minor?

The note that decides

You would. Major and minor live almost entirely in one note, the third.

A chord is a group of notes heard together as one harmony. We describe it from its root, the note that names it (C here). Count up from the root in semitones and you get its recipe:

• C major is C, E, G: root, a note 4 semitones up (the major third), and one 7 up (the fifth).
• C minor is C, E♭, G: the third drops to 3 semitones. Root and fifth don't change.

Three-note chords built this way are triads. The fifth adds body and stability. The root gives the chord its name and its weight. But the third is the one that tells your ear "bright" or "dark". Take the fifth away and C with E still sounds major; C with E♭ still sounds minor. Take the third away and you're left with C and G, which could be either. That's the power chord of rock guitar: it sounds huge partly because it refuses to commit, so it fits under any melody and distortion doesn't turn it to mush.

A tour of chords built on C

Each chord below changes one or two notes from plain C major. Let it loop and listen to how each one leans.

Chord	Notes	Semitones above C	How it tends to feel in pop and jazz
C	C E G	0 4 7	Settled, bright
Cm	C E♭ G	0 3 7	Settled, darker
Csus4	C F G	0 5 7	Hanging in the air, waiting to land
Cmaj7	C E G B	0 4 7 11	Soft, dreamy, a little wistful
C7	C E G B♭	0 4 7 10	Bluesy, restless, wants to move
Cm7	C E♭ G B♭	0 3 7 10	Smooth, mellow, at ease

A sus4 (suspended fourth) swaps the third for the fourth, F. With no third, it's neither major nor minor, and the F sits just above where E would be, so most ears hear it wanting to drop down into C major. That little tug, resolved or left hanging, is all over pop choruses and guitar intros.

Feelings in the last column aren't rules. A minor chord can be fierce, a major one heartbreaking; it depends on tempo, register and what comes before. But the recipes are the reason those moods are so easy to reach.

Two sevenths, two worlds

Add the seventh note of the scale above the root and you get a seventh chord. Which seventh you add changes everything, and the symbols are easy to mix up.

Cmaj7 adds B, a semitone below the octave. That B sits right next to the C above it and rubs gently against it, which is why maj7 chords sound soft-focus and nostalgic. They're the sound of bossa nova, a lot of neo-soul, and most lo-fi keys: a major chord that's still thinking about something.

C7 adds B♭ instead, and gets a dominant seventh. The E and B♭ inside it are six semitones apart, a tense interval called the tritone, and that tension wants to go somewhere. In a twelve-bar blues, all three chords are often played as dominant sevenths, so the whole form has that greasy, unresolved swagger.

Cm7 is a minor triad with B♭ on top: relaxed, warm, the default chord of a thousand smooth grooves.

The symbols are a trap: "7" alone means the B♭ version, "maj7" means B. A singer who asks for C7 and gets Cmaj7 will hear the difference immediately.

Leaving notes out

A chord symbol lists ingredients, not orders. Players leave notes out all the time.

The fifth goes first. It's in almost every chord, so it says little about which chord this is, and leaving it out makes room. Jazz pianists often go further and drop the root too, leaving it to the bass player: the rootless voicings Bill Evans made famous are mostly thirds, sevenths and colour notes. Remove the third, though, and you've removed the decision. Sometimes that's exactly the point, as with the power chord.

How little does a chord need? The opening chord of the Beatles' "A Hard Day's Night" is one loud strum, and musicians have argued for decades about exactly which notes are in it. People hear it, love it, and still can't agree what to call it.

Colour tones

Keep stacking and you reach extensions: the 9th (D above C), the 11th and the 13th. They don't change whether the chord is major or minor; they add shimmer. A 9th on a major chord sounds open and a little expensive, like a film's establishing shot.

Read the symbols carefully. Cadd9 is a triad plus D, no seventh. C9 includes the B♭ seventh as well, so it's bluesy. Cmaj9 includes the B. Same added note, three different chords.

Why a major chord sounds so natural

Play a single low C on almost any instrument and it contains a whole series of quieter, higher pitches called harmonics.

Harmonics 4, 5 and 6 sit in the ratio 4:5:6, which is very nearly C, E and G. A major triad is, in a sense, a thinned-out copy of a single rich tone. On a piano the match isn't exact: the piano's E is about 14 cents (a seventh of a semitone) sharper than the 5th harmonic, a compromise that the tuning systems guide explores. That's a physical relationship, not a proof that major chords are nicer; what sounds pleasant also depends on the music you grew up with.

Same idea, different place: Timbre and harmonics builds a single tone out of harmonics. Here you've built a chord out of tones. Sometimes they turn out to be the same picture.

Where the label stops helping

A chord's name describes what's in it. Its role comes from the music around it. G7 on its own is just a restless chord. After a C major passage, it sounds like it's pulling you home. In a blues in G, it is home. The ingredients are the same; the job is different.

And a sparse chord can be ambiguous. C and E alone could be the top of C major, or A minor with the A in the bass, or part of something stranger. When you want a clear message, make sure the third and the bass are both there. Chord-recognition software runs into exactly this ambiguity: Chord and key recognition shows why it often has two honest names for one sound, and why the bass usually decides.

Make it yours

Pick a root that isn't C. Build its major triad (0, 4, 7 semitones up), then a minor version, then one seventh chord of your choice. Play them in a loop and give each a one-word description of how it feels to you.

Now choose the one you'd put under the last line of a song, and the one you'd put under a question. If you want one key to play a whole chord while you explore, Maru's Chord tool turns each note you play into a major, minor, sus4 or seventh chord. Save the three recipes; they're the start of a progression.

Quick check

1. Which single note turns F major (F, A, C) into F minor? A drops to A♭. The third goes from 4 semitones above F to 3. It's tempting to change the root or the top note, but the third alone carries major and minor.
2. A chart says C7 and you play C, E, G, B. What's wrong, and will anyone notice? C7 means B♭, not B. You played Cmaj7, which sounds soft and dreamy instead of bluesy and restless. Yes, people will notice, especially over a blues.
3. A guitarist plays only C and G. Is it C major or C minor? Neither, yet. Without the third, the chord hasn't decided. A bass line, a melody note or the next chord can tip it either way, which is why power chords fit almost anywhere.

Next steps

• Go deeper: Chords and voicing. You can name the notes now. Where you put them decides whether the same chord sounds dreamy or muddy.
• Use it: Progressions and harmonic movement. Put chords in a row and make them go somewhere.