Chord Finder

A chord name is a shorthand for a set of pitches with a root, and the tool works in both directions. Select the keys you are holding and it names the chord, spells its notes and says which note is in the bass. Choose a root and a quality and it spells the chord and plays each of its inversions. Both directions use the same tables, so a name the tool gives is one you can look up on the reference pages.

#How a set of keys becomes a chord name

The tool does not look at octaves when it names a chord. It takes the pitch classes of the keys you select, the twelve note names without their register, and asks which chord types contain exactly that set. C4, E4 and G4 give the same set as E3, G3 and C5, and both name a C major chord. The match has to be exact. A set with a note no formula covers, such as C, E, G and F♯, gets no name rather than a guessed one.

Each chord type is a formula measured from the root. A major triad is the root, a major third and a perfect fifth. A dominant seventh adds a minor seventh to that. The tool tries each pitch class in the selection as a possible root, checks the formulas, and lists every reading that fits. Two notes a fifth apart name a power chord. Three notes name a triad or a suspended chord, and four notes name most sevenths.

#Root, bass and the slash

The root is the note the chord is built on. The bass is the lowest key you selected. When the two are the same note, the chord is in root position. When the bass is a chord tone other than the root, the name takes a slash: E, G and C with C as the root is C/E, a C major chord in first inversion. Root-position readings come before slash readings, since a chord is normally named by its root. The order you press keys in does not change the name, and neither does the octave, except that the lowest sounding note decides the bass.

#Spelling follows the letter names

A chord uses one letter name for each degree, so the spelling is more than the pitch. The tool tries each enharmonic name of the root and keeps the spelling with the fewest double sharps and flats. F♯ and G♭ are the same key, but an F♯ half-diminished seventh is spelled F♯, A, C and E, while the G♭ version needs B♭♭, D♭♭ and F♭. The first is what a reader expects, so the tool names the chord F♯m7♭5. The notes it shows under the name use the same spelling as the reference page for that chord.

#Ambiguous sets

Some sets have more than one honest name. An augmented triad divides the octave into three equal parts, so C, E and G♯ can be read as C augmented, as E augmented over its bass (written B♯, the same pitch as C), or as A♭ augmented over C. A diminished seventh chord divides it into four, which gives four readings for C, E♭, G♭ and A: C diminished seventh and three slash readings. The tool lists them all, with the root-position reading first. The notes cannot say which one the music intends; the chords before and after usually can.

Sixth chords create the most common ambiguity. C, E, G and A is C6, and it is also A minor seventh over C. Both readings are shown, and the one you choose depends on what comes before and after.

#Build a chord from a root and a quality

Build mode works the other way round. Pick a root and a quality, and the tool spells the chord from its formula, places the root between C3 and B3, and shows the notes as chips with the formula written with flat and sharp signs. A note that would sit more than a ninth above the root moves down an octave, so ninths and thirteenths stay on the keyboard.

Each inversion button moves one more of the lowest notes up an octave than the button before, so the first inversion moves the root and the second moves the root and the third. The chord is the same, but the bass changes. Play root position and the first inversion one after the other to hear the difference. The Play arpeggio button sounds the notes from the lowest upward.

#Using it well

Start from a shape you already know. Press the bottom note first, then add the others and read the result after each key. If the name changes, the new note is changing the chord, and you can see which one. If you want the other reading, choose it from the list of alternatives under the result.

If the name is not what you expected, check the keys you pressed, because one extra or missing note changes the set. C, E, G and B♭ name a C7. Add an A and the set matches no standard chord, so the tool says so rather than offering a name that leaves a note out.

#Limits

The tool names only the chord types in the reference tables, which are the triads, suspended and power chords, sixths, sevenths, ninths, the dominant thirteenth and the altered dominants 7♭9 and 7♯9. It does not name clusters, polychords or stacks built on fourths, and it does not recognise chords with an eleventh or a flat thirteenth. It keeps no record of voicing beyond the lowest key, so the same chord in close and open position gets the same name. The sound is a piano synthesiser in equal temperament, the tuning used by keyboards. The tool does not record, save or export anything.