The seven diatonic triads of C major
C major contains C, D, E, F, G, A and B, repeated in each octave. A triad uses the first, third and fifth notes counted from a chosen starting point within that collection. The notes stay inside the scale, but the distances between them are not identical for every root.
D–F–A is minor because D to F is a minor third. B–D–F is diminished because it includes a diminished fifth from B to F. The resulting pattern in a major key is major, minor, minor, major, major, minor, diminished.
| Degree | Chord | Notes |
|---|---|---|
| I | C major | C E G |
| ii | D minor | D F A |
| iii | E minor | E G B |
| IV | F major | F A C |
| V | G major | G B D |
| vi | A minor | A C E |
| vii° | B diminished | B D F |
Roman numerals describe relationships
Roman numerals show a chord’s position in a key. In the notation used here, uppercase numerals indicate major triads, lowercase indicate minor triads and a small circle indicates diminished. I–V–vi–IV in C major denotes C–G–Am–F.
The same pattern in G major is G–D–Em–C. Letter names change while the relationships remain. This makes numerals useful for comparing songs and moving an idea into another key. They describe how the chords relate to the tonic rather than fixing them to one pitch level.
A natural minor starts from a different tonic
A natural minor uses the same note collection as C major, beginning on A. Its diatonic triads therefore contain the same groups of pitches, now counted from another tonic. The pattern becomes i, ii°, III, iv, v, VI, VII.
The table describes natural minor specifically. Minor-key music often includes altered notes. An E-major chord in A minor contains G#, which is outside A natural minor. A diatonic table describes one collection; it does not prohibit chords drawn from other forms of the scale or other harmonic choices.
| Degree | Chord | Notes |
|---|---|---|
| i | A minor | A C E |
| ii° | B diminished | B D F |
| III | C major | C E G |
| iv | D minor | D F A |
| v | E minor | E G B |
| VI | F major | F A C |
| VII | G major | G B D |
Chord order and timing shape a progression
Am–F–C–G and Am–Dm–Em–Am both use the A-natural-minor collection. The second sequence returns explicitly to its opening Am, while the first reaches G before the next repeat. Their different routes create different patterns of departure and return.
Harmonic rhythm describes when chords change. Holding the first chord for two bars produces a different phrase from giving every chord equal time. The same chord names can therefore support a different sense of movement through duration, repetition and placement against the drums.
The chord collection connects separate parts
Over F major, F, A and C are direct choices for melodic chord tones, while a low F reinforces the root in the bass. Other scale notes create additional relationships. The value of the chart is that it identifies a clear reference point for understanding those choices.
Inversions and voicings offer further variation within a fixed progression. The notes can move smoothly between chords, spread across a wider register or form a more noticeable top line. A small diatonic collection can produce substantial variety before more complex harmony is added.