Chord Progression Analyzer
Enter a progression to estimate its tonal center, Roman numerals, harmonic functions, cadences, and likely chromatic interpretations.
Examples: C G Am F · Dm7 G7 Cmaj7 · Am F C G · C/G G7 C
Chord-by-chord analysis
Tap a card for detailsAlternative key fits
Harmonic tension
Automatic harmonic analysis is interpretive. Short, modal, chromatic, or tonic-ambiguous progressions can support more than one valid analysis.
Your chord progression is processed locally in your browser. No progression data is sent by this tool.
If the result looks unexpected, select a tonic or major/minor mode manually and analyze again.
Session history
Your recent analyses will appear here during this browser session.
A Chord Progression Analyzer helps you understand what a sequence of chords is doing harmonically—not just which chords are present. Enter a progression such as C – G – Am – F, Dm7 – G7 – Cmaj7, or Am – F – C – G, and the analyzer can identify the most likely key, translate the chords into Roman numerals, show harmonic functions, flag non-diatonic chords, and highlight possible cadences or chromatic movement.
This makes the tool useful for songwriting, music theory study, arranging, reharmonization, and analyzing chord sequences from songs. If you are still building a progression rather than analyzing one, start with the Chord Progression Calculator to create a sequence first.
How to Use the Chord Progression Analyzer
Enter your chords in progression order. Common chord symbols such as major, minor, seventh, suspended, sharp, flat, and slash chords can be analyzed when written in a recognizable format.
For example:
C – G – Am – F
or:
Dm7 | G7 | Cmaj7 | Am7
After entering the progression, run the analysis. The tool evaluates the chord collection and harmonic relationships, then returns the most likely tonal interpretation.
Your results may include:
- Most likely key
- Key fit score
- Alternative possible keys
- Roman numeral progression
- Harmonic function of each chord
- Diatonic or non-diatonic status
- Possible secondary dominants
- Possible borrowed chords
- Cadence information
- Chord tones
- Harmonic tension
- Transposed versions of the progression
If you already know the key, selecting it manually can help when a short or highly chromatic progression could reasonably be interpreted in more than one way.
How Chord Progression Analysis Works
A chord progression can be understood in two different ways: by its absolute chord names and by the role those chords play within a key.
Consider:
C – G – Am – F
In C major, those chords correspond to:
I – V – vi – IV
The chord names tell you what to play. The Roman numerals explain the harmonic structure.
This relative representation is useful because the same pattern can appear in many keys. In G major, for example, the same functional pattern would be:
G – D – Em – C
The actual chord names changed, but the underlying progression is still I – V – vi – IV.
You can explore this system further with the Roman Numeral Converter or read the detailed guide to Roman numeral chords.
Understanding the Most Likely Key
Automatic key detection compares the chords in your progression with the chords expected in possible major and minor keys.
A progression such as:
Dm – G – C
strongly points toward C major because the chords function naturally as:
ii – V – I
Other progressions are less definite. For example:
Am – F – C – G
can strongly suggest C major, but its opening and emphasis may also make A minor relevant depending on the melody, bass movement, phrasing, and where the progression resolves.
That is why the analyzer reports a key fit score and may show alternative candidates rather than claiming that every progression has one unquestionably correct key.
For a deeper explanation of identifying tonal centers outside the tool, see How to Find a Song Key.
How to Read Roman Numeral Results
Roman numerals represent scale degrees.
Uppercase numerals normally represent major-quality chords, while lowercase numerals usually represent minor-quality chords.
In a typical major key:
| Scale Degree | Common Chord | Roman Numeral |
|---|---|---|
| 1 | Major | I |
| 2 | Minor | ii |
| 3 | Minor | iii |
| 4 | Major | IV |
| 5 | Major | V |
| 6 | Minor | vi |
| 7 | Diminished | vii° |
For example, in C major:
C – F – G – C
becomes:
I – IV – V – I
Once you understand the Roman numerals, it becomes much easier to compare progressions across different keys and recognize recurring harmonic patterns such as the famous 1-5-6-4 chord progression.
Harmonic Functions: Tonic, Predominant, and Dominant
Roman numerals describe scale position, but harmonic function explains what a chord tends to do.
A simplified tonal model groups chords into three broad functions:
Tonic function creates stability or a sense of home.
Predominant function moves the harmony away from tonic and often prepares dominant harmony.
Dominant function creates tension that tends to resolve toward tonic.
In C major, a progression such as:
C – Dm – G – C
can be understood as:
I – ii – V – I
or functionally:
Tonic → Predominant → Dominant → Tonic
This functional view is especially useful when analyzing why a progression feels resolved, unfinished, tense, or directional.
The Circle of Fifths Progressions page can also help you see why certain chord movements naturally produce strong harmonic motion.
Diatonic and Non-Diatonic Chords
Not every chord in a progression has to belong strictly to the detected key.
A diatonic chord is built from notes belonging to the current key. A non-diatonic chord introduces one or more notes from outside that collection.
Non-diatonic chords can appear for many reasons, including:
- Secondary dominant harmony
- Modal mixture
- Borrowed chords
- Chromatic passing motion
- Temporary tonicization
- Key changes
- Reharmonization
For example, in C major:
C – A7 – Dm – G
the A7 chord contains C#, which does not belong to the C major scale. However, A7 strongly leads to Dm and may therefore be interpreted as a secondary dominant of ii.
The analyzer treats these labels as likely harmonic interpretations rather than forcing every chromatic chord into one category.
For more examples of harmony that remains mainly inside a key, compare the results with the guide to diatonic chord progressions.
Borrowed Chords and Chord Substitution
A progression can also borrow harmony from a parallel mode.
For example, a song in C major may use an F minor chord even though F minor is not part of the normal C major diatonic chord set. Depending on the surrounding harmony, that chord may function as modal mixture or a borrowed chord.
These colors are common in songwriting because they allow a progression to create emotional contrast without necessarily changing key completely.
Once you understand the existing harmonic structure, you can experiment with alternative harmony using the techniques covered in the Chord Substitution guide.
Cadences and Harmonic Resolution
A cadence is a harmonic arrival or stopping point.
The analyzer may identify likely cadence behavior when the final chords provide enough context.
Common examples include:
V → I— strong dominant-to-tonic resolutionIV → I— plagal-type resolution- Progressions ending on
V— often sound unresolved V → vi— can produce a deceptive-type resolution
Cadence detection depends heavily on context. A pair of chords does not always have one fixed interpretation, especially when the progression is modal, looping, or part of a longer musical phrase.
Transposing Your Progression
Once a progression has been analyzed, you can transpose it while preserving its harmonic relationships.
For example:
C – G – Am – F
transposed up two semitones becomes:
D – A – Bm – G
The chord names change, but the progression still follows:
I – V – vi – IV
For dedicated key changes, use the Chord Transposer, especially when you already know the destination key and mainly need the chord names converted.
Why Analyze a Chord Progression?
Analysis is useful when you want to move beyond memorizing chord names.
Songwriters can identify why a progression works and reuse the same functional structure in another key. Producers can inspect harmonic tension before arranging bass lines or melodies. Guitarists and pianists can understand the theory behind songs they already play. Students can compare actual harmony with Roman numeral concepts taught in music theory.
If you want to study the process in more detail, the Song Chord Analysis guide expands on how individual chords interact inside a complete progression.
Accuracy and Limitations
Chord progression analysis is contextual, so automatic results should be treated as likely interpretations, not absolute musical truth.
A short progression may fit several keys. Modal progressions may not behave like traditional major/minor harmony. Chromatic chords can have multiple functions depending on what comes before and after them.
Chord symbols also do not completely describe voice leading. For example, C → Am identifies two chords, but the actual movement of individual voices depends on the specific notes, inversions, registers, and voicings being played.
Melody, bass line, rhythm, phrasing, and musical form can also influence the true harmonic interpretation.
The analyzer therefore focuses on chord-symbol relationships and provides alternative interpretations where appropriate.
Privacy and Browser Processing
The Chord Progression Analyzer processes the progression directly in your browser. Entered chord progressions do not need to be uploaded to an external analysis service for the core calculations.
Browser-session history, when enabled, is intended to help you compare recent analyses during your current workflow. You can clear that history from the tool when you no longer need it.
Frequently Asked Questions
What is a chord progression analyzer?
A chord progression analyzer examines a sequence of chord symbols and identifies useful harmonic information such as the likely key, Roman numerals, chord functions, diatonic status, and possible chromatic relationships.
How do I find the key of a chord progression?
Look at which major or minor scale best explains the chords, then examine resolution points and dominant-to-tonic movement. The analyzer automates much of this comparison and shows the strongest candidate plus alternatives when appropriate.
Can one chord progression belong to multiple keys?
Yes. Many keys share chords, especially relative major and minor keys. Short progressions can therefore support multiple interpretations until melody, cadence, or additional chords establish a clearer tonal center.
What does I–V–vi–IV mean?
It represents chords built on the first, fifth, sixth, and fourth degrees of a key. In C major, those chords are C, G, Am, and F.
What is a secondary dominant?
A secondary dominant is a dominant-type chord that temporarily points toward a chord other than the main tonic. For example, A7 leading to Dm in C major can function as V/ii.
Can a progression contain chords outside its key?
Yes. Borrowed chords, secondary dominants, chromatic passing chords, modal mixture, and temporary key changes can all introduce notes or chords outside the basic diatonic scale.
Does the analyzer determine the exact theory behind every progression?
No. Harmonic analysis depends on musical context. The tool provides likely interpretations based on the chord symbols entered, while melody, bass movement, voicing, rhythm, and form can change how a progression is best understood.
Can I use the analyzer for songwriting?
Yes. Analyzing existing progressions can help you understand harmonic movement, transpose ideas, compare functional patterns, identify tension and resolution, and experiment with substitutions without simply copying chord names.