What Is a Triad? Major, Minor, Diminished and Augmented Triads

You find a chord chart with C, Cm, C° and C+ on it and your hand freezes over the keys, because each symbol asks for a slightly different shape. All four are triads, the three-note chords that almost every song is built from, and they share one recipe. Learn how the major triad, minor triad, diminished triad and augmented triad are stacked, and you can build any of them on any key in a few seconds.

Why triads are the chords to learn first

A triad is the smallest complete chord in Western harmony. The University of Puget Sound's theory text defines it as three notes stacked in consecutive thirds, and nearly every larger chord, from a seventh chord to a jazz voicing, starts from one of the four triad shapes and adds notes on top.

The four qualities are not equally common. The same text notes that major and minor triads are common, diminished triads less common and augmented triads rare. Learn major and minor first, then treat diminished and augmented as the two that bend the rule.

Root, third and fifth

The root, the third and the fifth each have one job. The root is the lowest note when the chord is stacked in thirds, and it names the chord; the third sits in the middle and decides major or minor; the fifth sits on top and, in major and minor triads, lies a perfect fifth (7 semitones) above the root.

Wikipedia's article on the triad gives the semitone formulas: 0–4–7 for major, 0–3–7 for minor, 0–3–6 for diminished and 0–4–8 for augmented. Those three numbers per chord are all the arithmetic you need.

How to build any triad, step by step

Building a triad takes five steps, and the order matters because the letters come before the accidentals.

1. Pick the root. Choose the note that names the chord, such as C for C, Cm, C° or C+. Find it on the keyboard; the guide to piano keys shows how to locate any white or black key from the groups of two and three black keys.
2. Write every other letter. Skip one letter each time: C, E, G, or D, F, A, or B, D, F. These letters are fixed for that root, whatever the quality of the chord.
3. Count the third. Count semitones from the root to the middle note: 4 for a major third, 3 for a minor third. Raise or lower the middle letter with a sharp or flat until the count is right, so C to E is 4 and C to E♭ is 3.
4. Count the upper third. Count from the middle note to the top note: 3 or 4 semitones again. The pair of thirds decides the quality: 4 + 3 is major, 3 + 4 minor, 3 + 3 diminished and 4 + 4 augmented.
5. Check the fifth. Add the two thirds and compare the total with the formula: 7 semitones for major and minor, 6 for diminished and 8 for augmented. If the total is wrong, one of the thirds is wrong.

Piano Companion does the checking for you. It shows 1,500+ piano chords with their notes, intervals, degrees and staff, plays inversions up to the 6th, and names any chord you press on its keyboard with "By keys"; then drop your triads into the progression builder and loop them.

The spelling step people get wrong

Step 2 is where most errors start, because on a keyboard E♭ and D♯ are the same black key. The chord still needs the E letter: C minor is C–E♭–G, and writing C–D♯–G turns the third into a second on paper, so the chord no longer reads as a stack of thirds.

The same rule gives the diminished triad a G♭ and the augmented triad a G♯. C diminished is C–E♭–G♭ (G♭ sounds like F♯), and C augmented is C–E–G♯ (G♯ sounds like A♭). Some roots force a double sharp or a double flat to keep the letters, so the fifth of G♯ augmented is D double sharp.

Major vs minor vs diminished vs augmented triads

The four triads differ only in their two thirds, and that difference shows in every column below.

Wikipedia's entry on the diminished triad confirms the two placements in the table: the seventh degree of a major scale, such as B–D–F in C major, and the second degree of a natural minor scale.

How each triad sounds

Play the four C triads in a row and listen to the middle and top notes move while C stays put. Major to minor lowers only the third, by one semitone; minor to diminished lowers the fifth as well; augmented goes the other way and raises the fifth of the major triad.

The Songtive chord pages let you see each one: C major and C diminished show the notes and every inversion on a keyboard diagram. To play the shapes yourself, the free online piano runs in the browser with no signup.

Triads in a major key

Every major key contains seven triads, one on each scale degree, and they follow a fixed pattern. Built only from the scale's own notes, they come out major, minor, minor, major, major, minor and diminished, which the Puget Sound text writes as the pattern M-m-m-M-M-m-°.

In C major the seven triads are C (I), Dm (ii), Em (iii), F (IV), G (V), Am (vi) and B° (vii°). Upper-case Roman numerals mark the major triads, lower-case the minor ones and the small circle the diminished one. The pattern is the same in all twelve major keys, so in G major the vi chord is Em and the vii° chord is F♯°.

No augmented triad appears in a major key. It turns up on the third degree of the harmonic minor scale, C–E–G♯ in A harmonic minor, though the augmented triad article notes that it virtually never occurs that way because of its harsh dissonance.

Triad inversions: root position, first and second

A triad inversion changes which note is lowest, while the chord's name stays the same. The Puget Sound chapter on inverted triads defines them by the bass note: root position has the root lowest, first inversion the third and second inversion the fifth.

For C major that is C–E–G, then E–G–C, then G–C–E. Inversions let you move between chords with small hand shifts, for example C (C–E–G) to F in second inversion (C–F–A) keeps your thumb on C. The chord inversions lesson works through the positions on the keyboard.

How to measure progress with triads

Progress with triads shows up as speed and accuracy on the three skills: spelling, playing and hearing. Test each one on a fixed schedule, such as every Sunday, and write down the numbers.

• Spelling speed: can you write all twelve major triads, root to fifth with correct letters, in under two minutes?
• Quality switch: can you play a major triad on any root, then turn it into minor, diminished and augmented without stopping?
• Key pattern: can you name the seven triads of C, G and F major, Roman numerals included, from memory?
• Inversions: can you play root position, first and second inversion of C, F and G major in a row, at a slow steady tempo?
• Ear: out of 20 triads played to you, how many qualities do you name correctly? Start by telling major from minor, then add the other two.

A two-minute daily test

Pick three random roots each day and run steps 1 to 5 on each one for all four qualities, twelve chords in total. Check each answer in the free chord finder: select the keys you hold down and it lists every chord those notes spell.

The chord exercises test the spelling side: they show a chord symbol and ask for its notes. For the ear, the post on telling major from minor chords covers the first distinction to master, major against minor.

Common triad mistakes

Most triad errors come from counting keys without checking letters, or from mixing up the two chords that change the fifth.

• Mistake: spelling by key instead of by letter. D♯ in place of E♭ in C minor is the same key and the wrong chord name. Write the letters first, then the accidentals.
• Mistake: confusing augmented and diminished. Augmented raises the fifth (8 semitones); diminished lowers the third and the fifth (6-semitone fifth). The symbol + means augmented and ° means diminished.
• Mistake: calling any inverted chord a new chord. E–G–C is C major in first inversion. Stack the notes in thirds to find the root before you name it.
• Mistake: forgetting the upper third. A correct third with a wrong fifth gives a different chord. Always run the fifth check from step 5.
• Mistake: expecting an augmented triad in a major key. The seven diatonic triads never include one, so a C+ in a C-major song is a chromatic chord.

The edge case: the augmented triad has no single root on the keyboard

The augmented triad divides the octave into three equal major thirds, so its keys repeat every four semitones. C augmented (C–E–G♯), E augmented (E–G♯–B♯) and A♭ augmented (A♭–C–E) use the same three piano keys.

Played alone, these three chords sound identical, and only the spelling and the music around them tell you which one is meant. When you see one of these in a score, read the letters to find the root.

Your triad checklist and next steps

• Recipe: you can say the four stacks of thirds, M3 + m3, m3 + M3, m3 + m3 and M3 + M3, without looking.
• Spelling: every triad you write uses every other letter from the root.
• Semitones: you check the fifth: 7 for major and minor, 6 for diminished, 8 for augmented.
• Key pattern: you can list I, ii, iii, IV, V, vi and vii° in at least three keys.
• Inversions: you can play root position, first and second inversion of the I, IV and V chords in C.

Once these are solid, move on to hearing the qualities quickly, then to seventh chords, which add one more third on top of the same triads. ChordIQ turns both halves into scored games: build the chord, name chord qualities by ear, and, with Pro, drill inversions and intervals, with a daily plan of three games picked from your weak spots.