A chord is three or more notes played together. Most chords begin as a triad: three notes stacked in thirds, called the root, the third and the fifth. From that one small shape come the bright chords and the dark ones, the tense ones, and the seventh and suspended chords behind nearly every song. Here is how a chord is put together, and the single note that turns it from major to minor.
Real theory, explained plainly. It works the same on a piano, a guitar, or in a piano roll, in any key and any style. Nothing here needs a particular instrument.
A chord is three or more notes played together. Two notes sounded at once make an interval; add a third note and you have the smallest thing most people would call a chord.
The most common chord by far is the triad, three notes named the root, the third and the fifth. Sound those together and you have a complete, stable chord. Almost everything else in this guide, the major and minor chords, the sevenths, the suspended chords, is that basic triad with one note added, swapped or moved.
A chord can hold more than three notes, and a piece will often spread one chord's notes across several octaves and instruments at once. But the identity of a chord is simply which notes are in it, not how high each one sits or how many times it is played. Get the three notes of the triad right and you have the chord.
Chords are built by stacking notes a third apart. Start on a note, skip the note directly above it, take the next one, then skip again and take the next. Those three notes, the root, the third and the fifth, are a triad.
A third here means two steps up a scale, roughly every other note. Stacking two of them gives the three notes of a triad, and the exact size of each third, whether it is a wider major third or a narrower minor third, decides what kind of triad you get. There are four ways the two thirds can stack, and they produce the four triad qualities.
| Triad | Stacked thirds | In C | Tends to sound |
|---|---|---|---|
| Major | Major third, then minor | C E G | Bright and settled |
| Minor | Minor third, then major | C Eb G | Darker and softer |
| Diminished | Minor third, then minor | C Eb Gb | Tense and unstable |
| Augmented | Major third, then major | C E G# | Restless and unresolved |
Major and minor are by far the most common; diminished and augmented turn up more rarely, used for tension and colour. Notice that the major and minor triads share the same outer notes and differ only in the middle one, which is the whole subject of the next question.
The same stacking builds the chords of a whole key. Take the seven notes of a scale and build a triad on each one, stacking thirds without stepping outside the scale, and you get the seven chords that naturally belong to that key. That is where a progression finds its chords. Our guide to scales and keys covers where those seven notes come from, and writing a chord progression takes the chords a key hands you and puts them in order.
The third does. A triad's middle note, its third, sits either a major third above the root, which sounds brighter, or a minor third above it, which sounds darker. That single note is the difference between a major chord and a minor one.
Take C major. Its three notes are C, E and G. The step from C up to E is a major third, the wider of the two, and that width is what gives the chord its bright, open sound. Now lower just the middle note by a semitone, from E down to Eb, and you have C minor: C, Eb and G. The root and the fifth have not moved at all. Only the third has slid down one step, and the whole chord turns darker and softer.
That is the pattern in every key: whether a chord is major or minor is decided by its third, so once you can find the third of a chord you can flip its mood by moving that one note up or down a semitone. Bright and dark are rough words for the effect, and the music around a chord can shade it, but as a first guide a major third sounds open and a minor third sounds shadowed.
They are triads with one note changed. A seventh chord stacks one more third on top of the triad; a suspended chord takes the third out and puts a neighbouring note in its place. Both start from the plain triad and give it a different flavour.
Keep stacking. Add one more note a third above the fifth and the triad becomes a seventh chord, four notes instead of three. That top note, the seventh, thickens the sound and is a staple of jazz, soul and R&B. Three are worth knowing:
A suspended chord removes the third, the very note that decides major or minor, and replaces it with a neighbour. A sus4 uses the fourth in its place (C F G in place of C E G); a sus2 uses the second (C D G). With no third at all, a suspended chord is neither major nor minor, so it sounds open and unfinished, as if waiting to settle onto an ordinary chord. That leaning quality is where the name comes from, and why a sus chord is so often followed by the plain triad it resolves to.
A chord keeps its identity no matter which of its notes is at the bottom. Play C, E and G with C in the bass and it is C major in root position; put E in the bass, or G in the bass, and it is still C major, just inverted. Same three notes, a different note underneath. An inversion does not change what the chord is, but it changes the chord's colour and, more usefully, lets the bass step in small moves from one chord to the next instead of leaping, which is much of what makes a run of chords flow.
We built ARGISH to make this quick to hear. It is a self-playing chord synth: set a key and it builds chords and whole progressions that stay in that key, so you can listen to how each one sounds and take the ones you like straight into your own track. It is a fast way to learn how chords actually sound, not just how they are spelled on the page.
It runs free in your browser to try, and installs as AU, VST3, AAX or a standalone app when you want it inside your own sessions.
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