What chord is this

What it does

You press a chord and it tells you what it is called: the symbol you write above a stave (Cm7, C7/E, C°7) and the name spelled out. It recognises triads and seventh chords, inversions included.

The bass decides

The root is looked for starting from the lowest note. That is not a convenience: it is what makes predictable the cases where the same set of notes has two names.

C D G is Csus2 with C at the bottom and Gsus4 with G at the bottom. Same three notes, two different chords, and the bass is what says which — exactly as the books do.

The diminished seventh is symmetrical: C E♭ G♭ A give the same intervals read from all four notes. With no rule you would pick a root at random out of four; with this one you pick the one underneath, which is how you would write it reading a score. The same holds for the augmented triad.

When the root is not in the bass, the symbol writes it with a slash: C/E is a C major with E underneath.

Two octaves, and they are needed

With one you cannot press an inversion: the first inversion of C major is E G C, and that C is above. On a single octave you would press the C below, that is root position — and the tool could never see an inversion, which is half of what it exists for.

When it does not recognise, it says so

A cluster of semitones does not become the nearest chord: it becomes «not recognised», and underneath is the number of distinct notes, which is what you need to see why. Fewer than three is not a chord — two notes are an interval, and an interval is called something else.

On spelling

The symbol uses a fixed spelling: B♭ and not A♯. Pressing the black key between A and B tells nothing about how you write that note — it depends on the key you are in, and there is no key here. Any choice would be an invention, so the commonest one is printed and the choice is declared.

What is not here

No ninths, elevenths, thirteenths. No altered notes (♭9, ♯11, ♭13). No sixths or six-nine chords. No chords of five notes and up. All of them are recognisable and they are another tool: here the list is closed, and what is not on it is said rather than approximated.

No microphone and no files: you press, it does not listen.

On the playback

It plays what you pressed, inversion included, and not an ideal voicing of the chord it recognised: if you look at C/E and hear a C major in root position, the tool is answering a different question from the one you asked.

About your data

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