Tool

Progression analyser

A sequence of chord symbols read in a key: degree, function, and what each chord is doing there.

Write the chord symbols separated by spaces and choose the key. Each chord is read as a degree of that key, with its function, and the reading says what it is doing there — diatonic, borrowed, a secondary dominant, a tritone substitution.

Chord symbolsKey

Symbol	Degree	Function	Reading
Cmaj7	Imaj7	Tonic	Degree Imaj7 of the harmonic field of C major.
A7	V7/ii	Dominant	Secondary dominant: it prepares degree ii7.
Dm7	ii7	Subdominant	Degree ii7 of the harmonic field of C major.
G7	V7	Dominant	Degree V7 of the harmonic field of C major.
Em7	iii7	Tonic	Degree iii7 of the harmonic field of C major.
Fm	iv	Subdominant	Borrowed from the parallel minor mode: it is the iv of C minor.
Cmaj7	Imaj7	Tonic	Degree Imaj7 of the harmonic field of C major.

Candidate keys

How many chords in the sequence belong to each key's harmonic field. It is a ranking, not an answer: the tool does not separate relatives, and a sequence that modulates belongs to more than one.

5 of 7
5 of 7
B♯ major 5 of 7
3 of 7
3 of 7

Read about

Roman numeral analysisThe notation that describes a chord by the position it occupies in the key rather than by the note it sits on.
Harmonic functionThe role each degree plays — tonic, subdominant, or dominant — and the tension that moves one to the next.
Diatonic harmonyThe chords that arise from stacking thirds on each degree of a scale, and why each quality lands where it does.
Secondary dominantsChords from outside the key that act as the dominant of some degree other than the first.
Modal interchangeChords taken from the parallel key, changing a degree's colour without changing the centre.
Tritone substitutionReplacing a dominant with the one a tritone away, which shares its inner tritone.
CadencesThe formulas that close a phrase, and the degree of finality each one delivers.