Chord Quality
“Major,” “minor,” “diminished,” “augmented” - these name a chord's quality, not its root. A quality is the pattern of intervals stacked on top of the root: major is a stack of a major 3rd then a minor 3rd, minor is the same two intervals in the other order. The root just says where the pattern starts; the pattern itself is what makes it major.
Independent of the tonic
Because quality is a pattern rather than a specific set of notes, it doesn't care what key you're in or which note you build it on. A major triad rooted on C and a major triad rooted on G are different chords - different notes, different sound in context - but the same quality, the same shape, just rotated to a different starting wedge.
The physics: the gaps don't move
Transposing a chord - sliding it to a different root - shifts every note by the same distance, so the gaps between the notes stay exactly the same. Those gaps are what your ear actually tracks: the frequency ratios between the notes of a major triad are the same whether it's rooted on C or G or any other note, which is why “major” is one recognizable sound rather than twelve unrelated ones. Quality is what survives transposition; root is what doesn't.
Named twice: a suffix, and a color
The app marks a quality two ways, and both stay fixed wherever the chord sits on the wheel: a color, and a suffix - shown here in both its long form and its symbol, the short form that actually gets attached to a chord name or roman numeral (covered in Roman Numeral Notation).
| Quality | Symbolic notation | Letter notation | |
|---|---|---|---|
| Major Triad | ___ | Maj | |
| Minor Triad | m | min | |
| Diminished Triad | ° | dim | |
| Augmented Triad | + | Aug | |
| Suspended 4th Chord | sus | sus4 | |
| Dominant 7th Chord | 7 | 7 | |
| Major 7th Chord | Δ7 | Maj7 | |
| Minor 7th Chord | m7 | min7 | |
| Half Diminished 7th Chord | ø7 | m7♭5 | |
| Diminished 7th Chord | °7 | dim7 |
The most symmetrical qualities - augmented and diminished 7th chords - take that rotation-independence a step further: not only does the quality stay the same when you transpose it, several of its own notes are equally valid roots for the identical shape. See Symmetry and Dissonance for why that makes them sound the way they do.