A triad is the most basic chord in music: three notes made of a root, a third and a fifth, built by stacking two thirds on top of each other. Nearly every chord you know starts life as a triad. There are four kinds, major, minor, diminished and augmented, and the small differences between them are what make a chord sound happy, sad, tense or strange. Here is how a triad is put together, the four qualities worked out from C, and why they are the building blocks of almost all music.
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 triad is a three-note chord, made of a root, a third and a fifth. It is built by stacking two thirds on top of each other, and it is the most basic and most common chord in music.
Start on any note, the root. Go up a third to reach the second note, then up another third from there to reach the third note. Those three notes together, the root, the third and the fifth, are a triad. Sound them at once and you have a complete, stable chord.
The triad is the smallest thing most people would call a full chord, and it is where nearly every other chord begins. Add a note, swap a note or move one, and you get the sevenths, the suspended chords and the richer harmonies, but underneath almost all of them sits a plain triad.
There are four types of triad: major, minor, diminished and augmented. Each one has a root, a third and a fifth, but the exact size of the third and the fifth changes from one to the next, and that is what gives each its own mood. Here they are worked out from C.
| Triad | Stacked thirds | Notes from C | Tends to sound |
|---|---|---|---|
| Major | Major third, then minor | C E G | Bright and happy |
| Minor | Minor third, then major | C Eb G | Darker and sad |
| Diminished | Minor third, then minor | C Eb Gb | Tense and unstable |
| Augmented | Major third, then major | C E G# | Strange and dreamlike |
A major triad is a root, a major third and a perfect fifth. In C that is C E G, and it sounds bright and happy, the plain, settled chord behind most cheerful music.
A minor triad keeps the same root and fifth but lowers the middle note, so it is a root, a minor third and a perfect fifth. In C that is C Eb G, just one note different from C major, and it sounds darker and sadder.
A diminished triad is a root, a minor third and a diminished fifth, which is the fifth pulled in by a semitone. In C that is C Eb Gb, and it sounds tense and unstable, as if it wants to move somewhere else.
An augmented triad is a root, a major third and an augmented fifth, the fifth pushed out by a semitone. In C that is C E G#, and it sounds strange and dreamlike, neither settled nor clearly sad.
Major and minor triads do almost all the work in popular music; diminished and augmented triads are rarer, kept mostly for tension and colour.
You build a triad by stacking two thirds. Start on the root, count up a third to the second note, then count up another third to the third note. The size of each third, measured in semitones, decides which of the four triads you get.
A third comes in two sizes. A major third is four semitones, the wider one; a minor third is three semitones, the narrower one. The perfect fifth that forms the outer note of a major or minor triad is seven semitones above the root. Change the sizes of the two stacked thirds and you change the whole chord. Worked out from C:
The three notes do not have to stay in that order. Play the same root, third and fifth with a different note at the bottom and you have an inversion: the same triad, reordered. C E G with E in the bass, or G in the bass, is still a C major triad, the same three notes with a different one underneath. An inversion does not change what the chord is, only which note sits lowest, which is handy for letting the bass move in small steps from one chord to the next.
Triads matter because they are the building blocks of almost every chord and progression in music. Learn to spot and build them and most other harmony falls into place.
The major and minor triads in particular do most of the work in popular music. Take the notes of a key and build a triad on each one, staying inside the key, and you get the small set of chords a song draws on; put those chords in an order and you have a progression. A huge amount of pop, rock and folk is little more than three or four plain triads in a loop.
Triads are also the starting point for richer chords. Stack one more third on top of a triad and it becomes a seventh chord, a four-note chord with more colour and a touch of tension. Keep going and you reach the ninths and beyond. Almost all of it grows out of the same three-note shape, which is why the triad is the first chord worth knowing well.
We built ARGISH to make this quick to hear. It is a self-playing chord synth: set a key and it voices triads and richer chords that stay in that key, so you can hear how a major, minor, diminished or augmented chord actually sounds and how one moves to the next. It is a fast way to hear these shapes rather than just read them 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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