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Note identifier · Reference entry

What chord is C–E–G–A?

The notes C, E, G, and A spell C Major 6 (C6) — C the root, E the 3rd, G the 5th, and A the 6th.

Ranked readings

Every chord these notes can spell, most complete first. The bass note anchors the root-position reading; each candidate maps every note to its scale degree.

C Major 6C6Confident

Every tone of C6 is present, with C in the bass — the definitive reading.

DegreeNoteIn this set
1Csounding
3Esounding
5Gsounding
6Asounding
A Minor 7thAm7Confident

All tones of Am7 are present; the C note is lowest (1st inversion).

DegreeNoteIn this set
1Asounding
♭3Csounding
5Esounding
♭7Gsounding
F Major 9thFmaj9Likely

3rd, 5th, 7th, and 9th of Fmaj9 sound; it reads as Fmaj9 with the F (1) omitted.

DegreeNoteIn this set
1Fomitted
3Asounding
5Csounding
7Esounding
9Gsounding
D 9sus4D9sus4Likely

4th, 5th, ♭7, and 9th of D9sus4 sound; it reads as D9sus4 with the D (1) omitted.

DegreeNoteIn this set
1Domitted
4Gsounding
5Asounding
♭7Csounding
9Esounding

Not these chords

Names these notes are often mistaken for. Each is ruled out because a defining tone of that chord is missing — the note that would make the name true simply is not being played.

Not C6/9

Not C6/9: a major 6/9 C chord needs D as its 9th — D is absent.

Not Am9

Not Am9: a minor 9th A chord needs B as its 9th — B is absent.

Not A7♯9

Not A7♯9: a dominant 7th ♯9 A chord needs C♯ as its 3rd — C♯ is absent.

Not Am7♭5

Not Am7♭5: a half diminished A chord needs E♭ as its ♭5 — E♭ is absent.

Not Am7♯5

Not Am7♯5: a minor 7♯5 A chord needs E♯ as its ♯5 — E♯ is absent.

How these notes relate

C, E, G, and A is a voicing of Fmaj9 with the F (root) left out.

The same notes over A in the bass spell Am7.

Add D (its 9th) and the set reads as C6/9.

Set-class analysis

The pitch-class set theory identity of these notes — order- and key-independent, computed from the set itself.

Pitch-class set
{0, 4, 7, 9}
Normal order
[4,7,9,0]
Prime form
[0,3,5,8]
Interval vector
<012120>
Forte set class
4-26

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