Lesson 13: Triads: Building Chords

When two or more notes sound together, they form a chord. Chords are the harmony of music: they support the melody, give it colour, and create the feeling of tension and release that drives a piece forward. The simplest and most important chord is the triad, built from just three notes.

A triad is built by stacking thirds. Start on any note — the root — then add the note a third above it, then the note a fifth above it. In the key of C major, the triad built on C is C-E-G: C is the root, E is the third, and G is the fifth. These three notes are called the root, third and fifth of the chord. Every triad in Western music is built this way, on any note of the scale, and the quality of the chord depends on the sizes of the two thirds stacked inside it.

Major, Minor, Diminished and Augmented

A major triad is built from a major third (4 semitones) on the bottom and a minor third (3 semitones) on top: root to third is major, third to fifth is minor. C-E-G is a major triad, and it sounds bright and stable. A minor triad reverses the order: a minor third (3 semitones) on the bottom and a major third (4 semitones) on top. C-E flat-G is a minor triad, and it sounds darker and sadder. A diminished triad stacks two minor thirds (3 + 3 semitones), giving a tense, unstable sound — B-D-F is diminished. An augmented triad stacks two major thirds (4 + 4 semitones), giving a strange, floating sound — C-E-G sharp is augmented. Major and minor triads are by far the most common; diminished and augmented triads are used more sparingly, usually to create tension.

Inversions: The Same Chord, Rearranged

A triad does not have to be played with the root at the bottom. If the third is the lowest note, the chord is in first inversion (E-G-C for a C major triad); if the fifth is the lowest note, it is in second inversion (G-C-E). The chord is still a C major triad — the same three notes, the same harmony — but the sound is subtly different, and the inversion matters for smooth voice leading: a melody or bass line can move by step from one chord to the next instead of jumping. Pianists and guitarists use inversions constantly to keep their hands in one position while the harmony changes underneath. In written music, inversions are shown with figured bass numbers: root position is 5/3, first inversion is 6/3, and second inversion is 6/4.

Seventh Chords and Chord Symbols

Triads are the foundation, but real music uses taller chords too. Add a fourth note a seventh above the root and you get a seventh chord. The most important is the dominant seventh: a major triad with a minor seventh on top, such as G-B-D-F in the key of C major. It sounds tense and pulls even more strongly back to the tonic than a plain dominant triad, which is why it appears at nearly every important cadence in classical and jazz music. Seventh chords are written with chord symbols in popular music: Cmaj7 means a C major triad with a major seventh, Cm7 means a C minor triad with a minor seventh, and G7 means a G dominant seventh. These symbols are the shorthand of jazz, pop and rock: a lead sheet gives the melody and the chord symbols, and the players invent their own voicings. The triads on each note of a minor scale have their own pattern too: in A minor they are Am, B diminished, C major, D minor, E minor, F major and G major. Compare that with C major's pattern and you will see they are the same chords in a different order — another sign that relative major and minor are two views of the same material.