A chord is three or more notes sounding together. Its quality (major, minor, diminished, augmented, and the seventh types) is a pattern of intervals your ear can learn in weeks.
The major triad stacks a major 3rd plus a minor 3rd (offsets 0-4-7); swap the order and you get minor (0-3-7). That single swapped third is the happy/sad hinge of Western music.
Seventh chords add one more third, and their five common qualities carry most of jazz and pop harmony. Inversions re-order the same notes with a different one in the bass; the quality survives, the color shifts.
Start with major versus minor only, played as block chords. Listen for the bright or dark third; ten minutes a day makes this reliable within a week or two.
| Quality | Offsets | On C |
|---|---|---|
| Major | 0 - 4 - 7 | C E G |
| Minor | 0 - 3 - 7 | C D♯ G |
| Diminished | 0 - 3 - 6 | C D♯ F♯ |
| Augmented | 0 - 4 - 8 | C E G♯ |
Common questions
What makes a chord major or minor?
The third. A major triad has 4 semitones between root and third; a minor triad has 3. The fifth is the same in both.
What are the main seventh chords?
Major 7th (0-4-7-11), dominant 7th (0-4-7-10), minor 7th (0-3-7-10), half-diminished (0-3-6-10) and diminished 7th (0-3-6-9).