Triads Explained: Major, Minor, Diminished, Augmented
By Solfa Theory · Published: 24 October 2026 · Updated: 24 October 2026
Quick answer: what is a triad?
A triad is a three-note chord: a root, a third and a fifth. Change the size of the third and fifth and you get the four types: major (4 + 3 semitones), minor (3 + 4), diminished (3 + 3) and augmented (4 + 4). Nearly every song you know is built from major and minor triads.
How a triad is built
Start on any note. That is the root, and it gives the chord its name. Skip one note of the scale and take the next: that is the third. Skip another and take the next: that is the fifth. Stacking notes in thirds like this is the foundation of Western harmony.
On the keys of a piano, C, E and G make a C triad. They are every other white key. If you are unsure what a third or a fifth is, intervals explained covers the distances between notes, and the free online piano lets you hear each one.
The four types of triad
The size of each third (measured in semitones, called half steps in the US) decides the chord type. Here they are built on C.
| Triad | Semitones (lower third + upper third) | Notes on C | Typical sound |
|---|---|---|---|
| Major | 4 + 3 | C, E, G | Bright, stable |
| Minor | 3 + 4 | C, E flat, G | Darker, more serious |
| Diminished | 3 + 3 | C, E flat, G flat | Tense, unstable |
| Augmented | 4 + 4 | C, E, G sharp | Dreamy, unresolved |
Notice how little changes. Going from major to minor lowers one note, the third, by a single semitone. That one move flips the mood of the chord, which is why the third is often called the most important note in a triad.
Major and minor: the two you will use most
A major triad stacks a major third and then a minor third. A minor triad does the reverse. Both share the same perfect fifth, so they blend well when one follows the other. If you want to hear the difference in action, our major vs minor scales guide explains how the same third shapes a whole scale.
Diminished and augmented: the spice
A diminished triad stacks two minor thirds. The fifth is flattened, so the chord feels like it wants to go somewhere. An augmented triad stacks two major thirds, which raises the fifth and leaves the chord floating. Both are rarer than major and minor, but they are useful for tension and for moving smoothly between chords.
The triads in a major key
Build a triad on each note of a major scale, using only notes from that scale, and you get the same pattern in every key. Roman numerals label each one: capital for major, lowercase for minor, and a small circle for diminished.
| Degree | I | ii | iii | IV | V | vi | vii° |
|---|---|---|---|---|---|---|---|
| Type | Major | Minor | Minor | Major | Major | Minor | Diminished |
| In C major | C | Dm | Em | F | G | Am | B dim |
This table is the secret behind most chord progressions. The popular I, V, vi, IV sequence is just C, G, Am and F in this key. See 7 chord progressions and how to write a chord progression to put these chords to work, and the chord and scale explorer to hear them.
Inversions: the same chord in a new order
You do not always play a triad with the root at the bottom. Putting the third or the fifth lowest gives you an inversion. It is the same chord with a different flavour, and it makes chord changes smoother under your fingers. Learn more in chord inversions made simple.
How to practise triads
- Play a major triad on C, then lower the middle note by one semitone to make it minor. Listen to the change.
- Do the same on five other starting notes.
- Play the seven triads of C major in order, saying the type of each out loud.
- Try identifying them by ear with how to identify chords by ear.
Ten minutes a day is plenty. Fit it into your week with the 15-minute daily practice routine. When triads feel automatic, add one more note and move on to seventh chords.
Common mistakes
Many beginners memorise chord shapes without knowing what is inside them. Shapes work on one instrument, but the formula works everywhere. Another is forgetting that a triad depends on the key: in C major, the chord on the second note is minor, not major. Count the semitones when in doubt.
Frequently asked questions
What is a triad in music?
A triad is a three-note chord made by stacking two thirds on top of a root note. The three notes are called the root, the third and the fifth.
What is the difference between a major and a minor triad?
Only the middle note changes. A major triad has a major third (4 semitones, or half steps, above the root). A minor triad has a minor third (3 semitones). The fifth stays the same, which is why the two chords sound related but have a different mood.
How many types of triads are there?
Four main types: major, minor, diminished and augmented. Major and minor are by far the most common in pop, rock and folk. Diminished and augmented triads add tension and are used more sparingly.
How do I find the triads in a key?
Build a triad on each note of the scale, using only notes from that scale. In any major key the result is the same pattern: major, minor, minor, major, major, minor, diminished.
Are triads the same as chords?
A triad is the simplest kind of chord. Many chords are triads with extra notes added, such as a seventh. Learn triads first and the larger chords make more sense.
What is the easiest way to remember triad formulas?
Count semitones. Major is 4 then 3. Minor is 3 then 4. Diminished is 3 then 3. Augmented is 4 then 4. Say them out loud while playing them on a keyboard.
Where to go next
Once you can build triads, the next steps are chord progressions and seventh chords. If you are starting out, music theory for beginners places triads in the full learning path.