Major and minor
The third is the tell. A major third reaches clockwise to M3; a minor third stops one step earlier at m3.
Chord qualities as interval shapes
Each chord is a polygon on the 12-tone circle. In Relative mode the root sits at the top so chords of the same quality share a shape. In Absolute mode the ring shows fixed pitch classes (C at the top) and the polygon rotates to where the chord's actual notes fall. The bass / inversion control changes naming and playback order; the polygon's shape stays the same. For voice leading and chord progressions, see Chord progressions.
Graphic grammar: pale chromatic ring, red root, black selected tones, translucent red-to-blue chord body.
Pitch labels
Wheel order
Chord Details
Intervals above root
Stack from bass
Bass
Recognized root
Symbol
Semitones above root
Forte prime form
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Interval-class vector
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Chord Quality
Play
Sonority (Plomp-Levelt / Sethares)
Sensory dissonance from the Plomp-Levelt curve (1965) as refined by Sethares (1993). Each tone is treated as a fundamental plus six harmonics (amplitudes 1/n); the curve plots how dissonant each interval is against a fixed reference tone. The vertical lines mark where this chord's intervals from the bass land on the curve.
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Key fit (Krumhansl-Kessler)
Correlation of this chord's pitch-class set against each of the 24 major and minor key profiles from Krumhansl & Kessler (1982). Outer ring: major keys; inner ring: minor. Dot size encodes fit strength; the top match is named in the center.
— probe-tone stability per scale degree (chord tones highlighted)
Common chords
Reading the shapes
Root and bass
The red P1 is the reference note. The recognizer can choose another selected tone as the chord root; the bass is the lowest played tone.
Suspensions
A sus chord removes the third. The replacement tone is either M2 or P4, so the triangle leans away from major/minor identity.
Altered fifths
Augmented and diminished chords move the fifth by one semitone. That shifts the triangle point from P5 to m6 or TT.
Sevenths
Four-note chords become quadrilaterals. The distance between the third, fifth, and seventh makes dominant, minor, major, and diminished seventh shapes easy to compare.
Tonic
Tonic is a key function, not a chord tone. This widget names roots and bass notes; it doesn't assign a key center.