How this instrument works
A triad is built from three notes stacked in thirds above a root: the root itself, a third, and a fifth. What distinguishes one chord quality from another is the exact size, in semitones, of those two upper intervals. A major triad stacks a major third (4 semitones) and a perfect fifth (7 semitones) above the root; a minor triad stacks a minor third (3 semitones) and a perfect fifth (7 semitones); a diminished triad stacks a minor third (3 semitones) and a diminished fifth (6 semitones); an augmented triad stacks a major third (4 semitones) and an augmented fifth (8 semitones).
Because every quality is defined purely by semitone distance from the root, the same four interval patterns apply no matter which of the twelve notes you start from — pick any root and quality, and the instrument counts up the chromatic scale by the right number of semitones for the third and the fifth. This is the same construction method taught in every introductory tonal-harmony course, sometimes called tertian (third-stacked) harmony.
This instrument outputs note names using sharps (for example D# rather than its enharmonic equivalent Eb), so the letter names it returns are always chromatically correct, even where a different key context might conventionally prefer flat spelling.
- Select Root note — any of the twelve chromatic notes.
- Select Chord quality — Major, Minor, Diminished, or Augmented.
- Read Chord tones directly beneath the inputs — three notes listed from root to fifth.
- Compare qualities on the same root to hear how a one- or two-semitone shift in the third and fifth changes the chord's character.
Worked example — C major triad
Select Root note = C and Chord quality = Major. The major pattern is 0, 4, 7 semitones: C itself (0), C plus 4 semitones lands on E, and C plus 7 semitones lands on G. Chord tones reads C, E, G.
C, E, G is the most elementary triad in tonal harmony — the 1st, 3rd, and 5th degrees of the C major scale, stacked using exactly the 0-4-7 semitone pattern the major-quality formula specifies.
Questions
How are the chord tones actually calculated?
The instrument starts from the chosen root note and counts up the chromatic scale by a fixed number of semitones for each chord quality: 4 then 7 semitones total for major, 3 then 7 for minor, 3 then 6 for diminished, 4 then 8 for augmented. Whichever notes land on those semitone counts become the chord's third and fifth.
Why does a diminished triad sound unstable compared to major or minor?
A diminished triad stacks two minor thirds on top of each other (root to third is 3 semitones, third to fifth is another 3), which produces a diminished fifth — a dissonant tritone-adjacent interval — between the root and the top note. That built-in tension is why diminished chords are typically used to create instability that resolves elsewhere, rather than as a stable resting point.
How does a minor triad relate to its relative major?
A minor triad and the major triad built a minor third below it share the same key signature — for example, A minor (A, C, E) is the relative minor of C major, and both keys use no sharps or flats. The triads themselves use different notes, but the scales they're drawn from are identical.
Does the tool show flats or sharps for chords that would traditionally use flats?
It always uses sharp spellings — for instance D# rather than the enharmonically identical Eb. The pitch is always correct; only the letter name may differ from what a key-specific flat spelling convention would traditionally use in written notation.
How do I turn a triad into a seventh chord?
This instrument builds three-note triads only. A seventh chord adds a fourth note, a third above the triad's fifth (a major, minor, or diminished seventh above the root depending on the chord type) — that extra interval isn't covered here, but the same stacked-thirds logic extends naturally to it.