Chords & Harmony

Stacking thirds

A triad is formed by stacking two thirds on a root note – that is, you skip a scale note each time. From C this gives C–E–G, the C major triad. The three notes are called the root, the third and the fifth.

Whether a triad sounds bright or dark is decided by the lower third. It is measured in semitones (st):

• Major: major third below (4 st), minor third above (3 st) – a brighter, “happier” sound (C–E–G).
• Minor: minor third below (3 st), major third above (4 st) – a darker, “more pensive” sound (C–E♭–G).
• Diminished: two minor thirds (3+3 st) – tense and restless, with a diminished fifth (C–E♭–G♭).
• Augmented: two major thirds (4+4 st) – floating, hard to place (C–E–G♯).

With major and minor the outer fifth is “perfect” (7 st) and gives a stable, resting sound. Diminished and augmented feel unstable, because their fifth is narrowed or widened – they call for resolution.

The seven chords of a key

If you build a triad from scale notes on every degree of a major scale, you get seven chords that all fit the key. In C major these are:

Upper-case Roman numerals stand for major, lower-case for minor, and the ° for diminished. The order major–minor–minor–major–major–minor–diminished is the same in every major key – only the note names change. Countless songs consist of nothing but these degrees; the progression I–V–vi–IV alone carries hundreds of hits.

Four notes and new positions

A chord keeps its name no matter which of its notes is at the bottom. If the root is at the bottom, it is in root position; if the third is at the bottom, in first inversion; if the fifth is at the bottom, in second inversion. Inversions make for smoother transitions, because fewer notes have to move far when the chord changes.

Stack another third on the triad and you get a seventh chord (four notes). The most important types:

• Dominant seventh (e.g. G7): major triad + minor seventh. Sounds full of tension and pushes strongly back to the tonic.
• Major seventh / maj7 (Cmaj7): major triad + major seventh. Soft, jazzy, floating.
• Minor seventh / m7 (Dm7): minor triad + minor seventh. Round and mild.
• Half-diminished seventh (m7♭5): diminished triad + minor seventh – typical in minor-key cadences.

How to read C, Cm, C7 and Csus

In songbooks and lead sheets, chords appear as short symbols above the notes. The logic is consistent:

• C – major triad (just the letter).
• Cm or Cmin – minor triad.
• C7 – major with a minor seventh (dominant seventh).
• Cmaj7 (also C△) – major with a major seventh.
• Csus4 – the third is replaced by the fourth; it likes to resolve into the third.
• C/E – C major with E in the bass (an inversion; the note after the slash is the bass note).

These shorthands are used internationally. Anyone who can read them can play the accompaniment to almost any pop or folk song without writing out every single note.

How tension and resolution arise

Within a key, chords have particular functions. Three are fundamental:

• Tonic (I): home, the point of rest – this is where the music feels “arrived”.
• Subdominant (IV): leads away from the tonic, opens up space.
• Dominant (V): creates tension and pushes back to the tonic – especially strongly as a seventh chord (V7).

The basic motion of harmony is the cadence: tonic → subdominant → dominant → tonic, in degrees I–IV–V–I. Ubiquitous in jazz and pop is the progression ii–V–I. Once you have these motions in your ear, you can immediately hear in many pieces “where the music wants to go”.

▶ Practise with Circle of Fifths Auto – over 30 chord types with fretboard display.

How to get chords into your fingers – and your ear

1. First learn the four most common major and minor triads of your favourite key securely before expanding.
2. Practise chord changes slowly and evenly – a clean change matters more than speed.
3. Play each chord one note at a time as well (arpeggiated) and listen for whether it is major or minor.
4. Accompany a familiar song with the progression I–V–vi–IV – recognising familiar patterns motivates and consolidates.

FAQ on chords