Chord progression composer
The composer suggests the next chord of your progression: you pick or play one or two chords, it works out the key and ranks the options by mood (happy, sad, tension, arrival, melancholy, epic, dreamy, suspense, mystery). Each suggestion comes with a chord diagram for guitar, ukulele and cavaquinho, and you can listen to the progression and take it to the backing track.
Pick or play one or two chords. The composer works out the key and suggests what comes next, based on the mood each chord usually creates.
Your progression
Play a chord and let it ring…
Start with a chord
Famous progressions that fit
Chords in the key
How the suggestions work
It all comes from music theory, with no randomness. The composer works out the key from the chords you played and looks at the role each chord has in it: the ones that feel like "home", the ones that build tension and ask to be resolved, and the ones borrowed from another key.
- Happy: Major chords: open, light, upward sound.
- Sad: Minor chords: introspective, wistful sound.
- Tension: Chords that ask to be resolved: they build expectation.
- Arrival: Coming home: closure and relief.
- Melancholy: Chords borrowed from the minor key: longing, nostalgia.
- Epic: Big moves, straight out of film scores and stadium rock.
- Dreamy: Major sevenths and ninths: smooth, sophisticated, bossa nova.
- Suspense: Suspended chords: neither major nor minor, left hanging in the air.
- Mystery: Augmented and diminished chords and chromatic moves: unstable, intriguing.
Major chords sounding happy and minor chords sounding sad is a convention of Western music, not a law. Context, melody and rhythm change everything. Use the suggestions as a starting point and trust your ears.
Roman numerals: I, IV, V, VIm
Each chord is described by its degree in the scale of the key: I is the tonic (the "home" chord), IV is the subdominant, V is the dominant. An uppercase numeral means a major chord, an "m" after the number means minor, and ♭ marks a lowered degree borrowed from the parallel key. In C major, I–V–VIm–IV becomes C–G–Am–F; in G major, the same idea becomes G–D–Em–C. That is why the composer works in any key: the progression stays the same, only the names change.
Frequently asked questions
How does the composer find the key of the song?
It compares the chords you chose against all 24 keys (12 major and 12 minor) and checks which one each chord fits best, giving extra weight to the first and last chord. The most likely key appears with a confidence percentage, and you can switch to another reading with one tap.
Why do major chords sound happy and minor chords sad?
It is a convention of Western music, built over centuries of habit: the major third sounds open and bright, the minor third sounds darker and more inward. It is not a law: rhythm, melody and context can flip the effect. That is why the moods are starting points, not rules.
Are the suggestions generated by artificial intelligence?
No. They are music theory rules: the role of each chord in the key, cadences, chords borrowed from the parallel key, secondary dominants and suspended chords. The result is always the same for the same progression, and every suggestion comes with an explanation of why.
Can I play my instrument instead of picking the chord?
Yes. Tap "Play on your instrument", allow the microphone and let the chord ring. The composer recognizes the chord and you confirm it with "Use". The sound is analyzed inside your browser and is never recorded or sent anywhere.
Can I take the progression to a backing track?
Yes. Once there is a chord in your progression, the "Build a backing track" button opens the backing track with the same chords, ready for you to play over.
Keep learning
Take your progression further: see the chord diagrams, hear it over a backing track and find scales to improvise on top.