Chord Finder (name a chord from its notes)

Understanding the chord finder — concept and principle

This tool names a chord from the notes you type, lowest note first. It is handy when you have worked out notes by ear, found a shape on the guitar or piano and want to know what it is called, or need to write a chord symbol on a lead sheet.

How it is calculated

1. Each note is turned into a pitch class from 0 to 11 (C = 0, C♯/D♭ = 1, … B = 11), so enharmonic spellings count as one sound. Repeated notes are removed.
2. At least three different pitch classes are needed.
3. Every note is tried in turn as the root. The distances in semitones above it are compared with the patterns of common chords: triads, sus2 and sus4, 6ths, 7ths and 9ths.
4. Every match is kept. The name whose root is the lowest note comes first; other valid names are listed after it.
5. The first note you typed is the bass. If it is not the root, the chord is written as a slash chord and the inversion is named.

The principle

A chord's identity depends on the set of pitch classes, not on octave or order. Once the notes are reduced to numbers 0–11, finding the chord is a matching problem: shift the set so a candidate root sits at 0, then see whether the remaining distances match a known pattern. A major triad is {0, 4, 7}, a minor triad {0, 3, 7}, a dominant seventh {0, 4, 7, 10}. Some sets match more than one pattern. C–E–G–A is both C6 and Am7, so the context, especially the bass note, decides which name a musician uses.

Worked example

Default input: E G C.

1. Pitch classes: E = 4, G = 7, C = 0; three different notes.
2. Try C as root: E is 4 and G is 7 semitones above C, giving {0, 4, 7}, a major triad.
3. Try E or G as root: the distances do not match any stored pattern.
4. The bass (first note) is E, the 3rd of C major.
5. Result: C/E, a major triad with root C, first inversion (3rd in the bass), no other names (—), 3 different notes.

How to read the result

The main name is what most players would write. A slash means the bass is not the root: C/E is C major with E at the bottom. First inversion sounds lighter than root position; second inversion (5th in the bass) sounds unsettled and often leads to a cadence. If alternative names are listed, choose the one that fits the key and where the music is going.

Common mistakes

• Typing the notes in any order and getting a slash chord you did not expect; the first note is treated as the bass.
• Entering only two notes; an interval alone is not a chord.
• Writing B as H or using solfège names; use letters A–G with # or b.
• Expecting extended chords such as 11ths or 13ths, which this tool does not list.

Frequently asked questions

What chord is E G C?

C major with E in the bass, written C/E (first inversion).

Why does my chord have two names?

Some note sets are shared. C–E–G–A is C6 and also Am7/C; the bass and the musical context decide.

Can I type flats and sharps?

Yes. Use # or ♯ for sharps and b or ♭ for flats, for example F# A D or Bb D F.

Sources: S. Kostka, D. Payne & B. Almén, Tonal Harmony, 8th ed. (McGraw-Hill, 2018), ch. 3–4 · M. Levine, The Jazz Theory Book (Sher Music, 1995), ch. 1–2