The Lab · Chord Rosetta
← Back to Chord RosettaChord Rosetta answers one question — what is this chord? — in more ways than most people know exist. This page walks through every part of what it tells you, in plain language, and points you somewhere trustworthy to read more. You don't need any of it to enjoy the tool; treat this as a map you can consult whenever a word on the screen makes you curious.
Nothing here is required reading. Play a chord first, then come back and look up whatever caught your eye.
There are two ways to hand Chord Rosetta a chord. You can play the on-screen piano, or you can type note names into the box — something like C4 E4 G4 B4, where the number is the octave. Any chord from two to twelve notes works.
One control is easy to miss and matters more than it looks: double-click a black key to flip how it's spelled — G♯ becomes A♭ and back. Those are the same key on a piano but not the same note on paper, and the spelling changes the reading. The very same keys can be a ♯5 in one spelling and a ♭13 in another. Chord Rosetta respects the spelling you choose.
Every chord also gets its own link — add ?notes=C4,E4,G4 to the address, or &lens=forte to open a particular reading first. Nothing is saved and nothing is tracked.
Before any of the deeper readings, you get the plain answer: the chord's name, its inversion, its notation on a staff, and its sound, so you can hear the thing you just built.
Here is the idea that makes Chord Rosetta different from an ordinary chord-namer. A chord doesn't have one true description — it has many, all correct at once. So instead of picking one, the tool shows you thirteen, and ranks them by how much each one actually tells you about the chord in front of you. It's the prism sorting its colours: the brightest, most revealing band goes to the front; the readings that add little get tucked to the side, each with a one-line reason for where it sits.
A plain C-major triad, for instance, fits so many keys that its Roman numeral tells you almost nothing on its own — so that reading gets demoted. A dense six-note cluster has no tidy chord symbol at all, so its set-theory “fingerprint” gets promoted to the top. Two views let you choose how much to see: Guided shows the answer and the readings that matter; Everything open lays out all thirteen at once.
It won't fake an answer. If a name only half-fits — say a chord symbol that leaves one note unexplained — the tool says so, and marks the match as partial rather than pretending it's clean. Honesty about what a reading can't tell you is part of the point.
Group A
What a working musician would actually call the chord — the labels you'd write on a lead sheet or say out loud at a rehearsal.
The ordinary chord symbol and everything packed into it: the root (the note it's named for), the quality (major, minor, diminished, augmented, seventh…), and the inversion.
The same notes as a jazz or pop musician might write them — often several defensible ways at once, because lead-sheet spelling is a language of shorthand and choice.
Chords that reach past the basic triad — ninths, elevenths, thirteenths — plus the “suspended” chords that swap the third for a nearby second or fourth, and “add” chords that drop an extra note in.
Group B
Not what the chord is in isolation, but how it sits, where it might go, and how it connects to its neighbours.
A chord's address within a key. Where a chord symbol tells you what the chord is, a Roman numeral tells you where it lives and why it might move — the same I–IV–V grammar in every key.
A way of describing how one triad glides to another by moving a single voice a step or a half-step. Three basic moves — P, L, and R — connect major and minor triads in the smooth, surprising ways you hear in film scores and late-Romantic music.
Not the chord's name but its layout: how far apart the notes sit, whether it's bunched up or spread out, and whether any note is doubled. Spacing is a big part of why two chords with the same name can sound completely different.
Most chords are built by stacking thirds. These are built by stacking fourths (quartal) or fifths (quintal) instead — the open, modern, slightly unmoored sound of a lot of jazz piano and film music.
Group C
Ways of describing a chord that ignore keys and styles entirely and look only at its raw shape — most useful for chords too strange for an ordinary name.
A method for naming any collection of notes by its abstract shape, invented to handle music that doesn't play by tonal rules. Every possible chord gets a catalogue number and a compact “fingerprint,” regardless of key or spelling.
The composer Paul Hindemith built his own system that sorts every chord into groups by how tense it is and whether it contains the restless tritone — a single ladder of tension from sweet to harsh, with a clear “root” for chords that tonal theory leaves ambiguous.
A chord heard as two simpler chords stacked on top of each other — one triad riding above another. It's how a thick, ambiguous sonority often makes the most sense: not one exotic chord, but two familiar ones at once.
Group D
Less about structure, more about the chord's character: how rough or smooth it sounds, which scales it lives inside, and where you'd actually meet it in the wild.
A measure of how rough the chord sounds to the ear — not whether the theory calls it a dissonance, but the physical grind produced when close-together tones beat against one another. It's consonance and dissonance measured as sensation rather than rule.
Which scales and modes the chord fits inside. A single chord can belong to many scales at once, and knowing which ones is how improvisers decide what to play over it.
Where the chord actually lives — the genres, eras, and players who lean on it. This is the reading that turns a bare label into a sound you recognise.
That's the whole instrument panel.
Now go play the prettiest chord you know — and the ugliest — and watch which colours the prism shows you.
Open Chord Rosetta →