1. The tonic
The tonic (also called root or fundamental) is the base note of a chord, the one that gives the chord its name.
Try C major and C minor chords →In a C major chord (C-E-G), the tonic is C.
In an F minor chord (F-A♭-C), the tonic is F.
2. Intervals
An interval is the distance between two notes, measured in semitones (each piano key, white or black, = 1 semitone).
| Interval | Semitones | Example (from C) | Color |
|---|---|---|---|
| Unison | 0 | C → C | Identical |
| Minor second | 1 | C → D♭ | Very dissonant |
| Major second | 2 | C → D | Gentle dissonance |
| Minor third | 3 | C → E♭ | Sad (base of minor chords) |
| Major third | 4 | C → E | Happy (base of major chords) |
| Perfect fourth | 5 | C → F | Open, stable |
| Tritone / dim. fifth | 6 | C → F♯ / G♭ | Very dissonant (devil's interval) |
| Perfect fifth | 7 | C → G | Stable, powerful |
| Aug. fifth / min. sixth | 8 | C → G♯ / A♭ | Tense / softly sad |
| Major sixth | 9 | C → A | Sweet, nostalgic |
| Minor seventh | 10 | C → B♭ | Bluesy, soulful |
| Major seventh | 11 | C → B | Reassuring, jazzy |
| Octave | 12 | C → C (higher) | Same note, higher |
| Ninth | 14 | C → D (higher) | Rich, open |
3. Building a chord
A chord is built by stacking notes on top of the tonic at specific intervals. Each note plays a role:
| Position | Role | Effect |
|---|---|---|
| Tonic (1) | Root note | Gives the chord its name |
| Third (3) | Determines major or minor | Major = happy, Minor = sad |
| Fifth (5) | Chord stability | Perfect = stable, Dim/Aug = unstable |
| Seventh (7) | Color / tension | Adds richness and motion |
| Ninth (9) | Airy extension | Jazzy, cinematic sound |
4. Major vs minor third
This is THE fundamental difference between a happy chord and a sad one.
Major third (4 semitones)
- C → E
- Path: C → C♯ → D → D♯ → E
- = 2 whole tones
- Sound: happy ☀️
Minor third (3 semitones)
- C → E♭
- Path: C → C♯ → D → E♭
- = 1 whole tone + 1 semitone
- Sound: sad 🌧️
5. Types of fifths
The fifth determines the stability of the chord.
| Type of fifth | Semitones | Example (C) | Usage |
|---|---|---|---|
| Diminished (♭5) | 6 | C → G♭ | Dim chords (unstable, dark) |
| Perfect | 7 | C → G | Major and minor chords (stable) |
| Augmented (♯5) | 8 | C → G♯ | Aug chords (tense) |
6. Types of sevenths
| Type | Semitones | Example (C) | Typical chord |
|---|---|---|---|
| Minor (♭7) | 10 | C → B♭ | C7, Cm7 (bluesy, soul) |
| Major | 11 | C → B | Cmaj7, Cm(maj7) (reassuring) |
Note: the dominant seventh (C7) = major third + minor seventh. The most used chord in blues/jazz because it creates tension that calls for resolution.
Try maj7, m7 and dominant 7 →7. Suspended chords (sus2, sus4)
In a suspended chord, the third is replaced by a second (sus2) or a fourth (sus4). The chord becomes neither major nor minor, it is "suspended" in a more neutral color.
- Csus2 = C + D + G (third replaced by 2nd)
- Csus4 = C + F + G (third replaced by 4th)
Often used to create tension before "resolving" onto the regular chord (sus4 → major is a very classic motion).
Try sus2 and sus4 →8. Power chords (5)
A power chord is the tonic + perfect fifth, no third. Since there's no third, the chord is neither major nor minor, it's neutral.
Widely used in rock/metal because the sound is punchy and compatible with guitar distortion (full chords sound "muddy" with heavy distortion).
Try power chords →9. Going further: modes
All these chords exist in every key (major, minor). The same construction formula (e.g., Root + Third + Fifth) applied to a different note gives a different chord.
Progression in C major →Major formula (0-4-7) applied to:
- C → C-E-G (C major)
- F → F-A-C (F major)
- G → G-B-D (G major)
- A → A-C♯-E (A major)