Automatic Chord Analysis

Chords submitted

Automatic Chord Analysis

ACA helps you analyze a chord. All possible degrees and keys are given, as well as the type of chord and the chord symbol.

I, II, III, IV, V, VI and VII (European notation) are degrees. Dominant 7th-2nd inversion and half diminished 7th-1st inversion are chord types. A7/E is a chord symbol.

The database consists of 12 x 16 keys, 312 chord types and 13,884 chords.


Tap BASS and then a piano key to select the lowest tone. Tap the other keys to select the remaining notes. Deselect by touching a key again.Tap/click CLEAR to reload the app, all previous selections will be reset.

The order of entry is not important. Just make sure the bass tone is correct.

Ignore ornamental tones like an appoggiatura. A chord consists of a minimum of 2 notes (incomplete chord) and a maximum of 5 notes (9th chord).

Tap ANALYZE to start the analysis.


Example chord: C (Bass) - Eb - G - A

*** Bb Major
VII6/5, half diminished 7th, 1st inversion
C•Eb•G•A, C is bass, A is root, symbol is Am7b5/C
** Ab Major Neapolitan (lowered 2)
III7, minor diminished 7th,
C•Eb•G•Bbb, C is bass, C is root, symbol is Cmb7

The stars indicate the probability. *** = probably, ** = less likely, * = rare. In this case VII6/5 in Bb Major is probably right. However, the app can't detect how original or difficult the score is, so always be on your guard.

An UNKNOWN chord can be a chord with an ornamental tone or an inverted (incomplete) 9th chord. Inversions of 9th chords are theoretically impossible.

These 16 key types are being used:

Major Neapolitan (lowered 2)
Major Neapolitan (low. 2 and low. 6)
Major Moll-Dur or Borrowed Chord (low. 6)
Major Moll-Dur or Borrowed Chord (low. 6 and low. 3)
Major + raised 2
Major Moll-Dur or Borrowed Chord (low. 6) + raised 4
Major Moll-Dur or Borrowed Chord (low. 6 and low. 3) + raised 4
Minor Natural
Minor Harmonic
Minor Melodic
Minor Natural + Neapolitan (low. 2)
Minor Harmonic + Neapolitan (low. 2)
Minor Melodic + Neapolitan (low. 2)
Minor Natural + raised 4
Minor Harmonic + raised 4

You can not use this app to analyze church modes like Dorian or Lydian. However, chords that are being called 'Phrygian' usually are Neapolitan chords.

The same applies to so-called 'special' keys, which are often major or minor keys with an incidental alteration.

In the above 16 keys all chords can be analyzed, unless you make up a chord yourself, and even then you'll be suprised when you analyze your chord with this app.

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