Triads
A triad is a three-note chord built by stacking thirds. There are four main types of triads, each with a distinct quality determined by the intervals between its notes.
| Type | Formula | Intervals | Example (C) | Sound Quality |
|---|---|---|---|---|
| Major | 1 – 3 – 5 | M3 + m3 | C – E – G | Bright, happy |
| Minor | 1 – ♭3 – 5 | m3 + M3 | C – E♭ – G | Dark, sad |
| Diminished | 1 – ♭3 – ♭5 | m3 + m3 | C – E♭ – G♭ | Tense, unstable |
| Augmented | 1 – 3 – ♯5 | M3 + M3 | C – E – G♯ | Mysterious, unsettled |
Chords in a Key
In any major key, each scale degree produces a specific chord quality. The pattern is always the same: Major, Minor, Minor, Major, Major, Minor, Diminished.
| Roman Numeral | Degree | Chord in C Major | Quality |
|---|---|---|---|
| I | Tonic | C Major | Major |
| ii | Supertonic | D Minor | Minor |
| iii | Mediant | E Minor | Minor |
| IV | Subdominant | F Major | Major |
| V | Dominant | G Major | Major |
| vi | Submediant | A Minor | Minor |
| vii° | Leading Tone | B Diminished | Diminished |
Tip: Roman numeral analysis works in every key. Capital numerals = major chords; lowercase = minor; ° = diminished.
Cadences
A cadence is a two-chord progression that creates a sense of pause or resolution at the end of a phrase.
| Cadence | Chords (in C) | Progression | Effect |
|---|---|---|---|
| Perfect | V – I | G → C | Strong resolution, conclusive |
| Imperfect (Half) | … – V | C → G | Unresolved, expects continuation |
| Plagal | IV – I | F → C | “Amen” cadence, gentle |
| Interrupted | V – vi | G → Am | Surprising, deceptive resolution |
Inversions
An inversion changes which note of the chord is in the bass (lowest position), altering the chord's voicing and feel.
| Inversion | Bass Note | Symbol (C Major) | Notes |
|---|---|---|---|
| Root Position | Root | C | C – E – G |
| 1st Inversion | 3rd | C/E | E – G – C |
| 2nd Inversion | 5th | C/G | G – C – E |
Note: Inversions are commonly used in voice leading to create smoother bass lines and more connected chord progressions.