A chord is a group of pitches heard or understood as one harmonic unit. A triad contains three different note names built by stacking two thirds. Triads underpin countless pop, electronic, rock, ambient and film compositions.
Root, third and fifth
A root gives a chord its name. The third helps determine whether a conventional triad is major or minor, while the fifth completes the structure. From C major, selecting scale degrees 1, 3 and 5 gives C–E–G. Those numbers are scale positions, not semitone counts.
Major triads
A major triad is built from a major third (four semitones) followed by a minor third (three semitones), giving a perfect fifth seven semitones above the root. C major is C–E–G. D major is D–F♯–A. F major is F–A–C. A major is A–C♯–E.
Minor triads
A minor triad reverses the thirds: three semitones then four, still ending on a perfect fifth. C minor is C–E♭–G; D minor is D–F–A; A minor is A–C–E. Moving E down to E♭ in C–E–G changes C major into C minor without altering root or fifth.
Diminished and augmented triads
Diminished triads stack two minor thirds and have a diminished fifth, six semitones above the root: C–E♭–G♭. Augmented triads stack two major thirds and have an augmented fifth, eight semitones above the root: C–E–G♯. These four basic qualities provide contrasting interval structures.
Spell the chord correctly
D major is D–F♯–A, not D–G♭–A, even though F♯ and G♭ sound equivalent on an equal-tempered keyboard. The third above D must use the letter F. Likewise the fifth of C diminished is G♭, not F♯. Spelling shows each note’s structural role.
Block chords, broken chords and arpeggios
A block chord sounds several pitches together. An arpeggio presents chord tones successively, such as C–E–G–E across four beats. The underlying note collection stays the same while the musical texture and rhythm change. Synth arpeggiators exploit this distinction by turning chord shapes into repeated patterns.
In Logic Pro or another DAW
Place three MIDI pitches at the same time in a Piano Roll to hear a block triad. Stagger their start positions to hear an arpeggio. Then compare C–E–G with C–E♭–G while keeping the rhythm and instrument unchanged. This makes the one-semitone quality change easy to hear.
Explore related articles in How Music Works — Volume 2.