How to name a chord from its notes

Most chords are built by stacking every other note: C, skip D, E, skip F, G. Each of these gaps is a third. So to name a chord you don’t recognise, put its notes back in that order, whatever order you played them in. The note at the bottom of the stack is the root, the one that gives the chord its name.

Below, the keyboard holds E, G and C. Stacked in thirds, they read C E G: a C major chord. But the lowest key you pressed is E, not C, so the name is written C/E, said “C over E”. The letter after the slash is the bass, the lowest note.

Now try it: add the C just below E. The name becomes plain C, because the root is now in the bass. Remove that C and add the G below instead: you get C/G. Three notes, one chord, three ways to write it, depending only on the lowest key.

Some groups of notes can be stacked in thirds in two ways. C, E, G and A are a good example: from C, they read as C6 (C major with an added sixth, A); from A, they read as Am7 (A minor with a seventh, G). Both are correct. The keys are the same, apart from where the A sits.

Listen to where each version rests: on C, then on A. That is why the chord finder puts the reading with the root in the bass first, and shows the other one after “It can also be read as”. With C at the bottom, you get C6, then Am7/C. Move the A below the C and the order flips: Am7 first, then C6/A.

The tool doesn’t know the piece you are playing, though. In a song that keeps coming back to A minor, Am7/C may be the more useful name, even with C in the bass. Read the list as possibilities, and let the music around the chord choose.

Pianists often leave a note out, especially in four-note chords, where the hand is busy. The note that goes first is usually the fifth: it adds little colour, while the third and the seventh say whether the chord is major or minor and what kind of seventh it has.

Compare C7 played in full, C E G B♭, with the same chord without its G. The colour barely changes. If you enter C, E and B♭, the chord finder still names C7 and adds a line to say that G is not played.

One limit to keep in mind: with three notes, a complete chord always comes first. C, E and A make a full A minor chord, so the tool reads Am/C before C6 without its fifth. And when the notes don’t form any common chord, C E F G for instance, it says so and suggests the closest one: C, with F added.

Before checking with the tool, try the method by hand: put the notes in thirds, find the root, then look at the bass. Each answer below is the name the chord finder gives for these exact keys.