Tools
Key Finder
Enter the chords of a song or progression and the key finder lists the keys that contain them, ranked by how well they fit. For each candidate you see every chord as a Roman numeral, which tells you its function, plus the scale you can use to improvise or write a melody. It runs in your browser.
How to use it
- Enter the chords in order, for example: Am F C G.
- Read the ranked list of possible keys.
- Check the Roman numerals for each chord in the top key.
- Look at chords marked as outside the key (borrowed or secondary).
- Click a key to open its scale and chord overview.
How the key is found
Every major key has seven diatonic chords: I, ii, iii, IV, V, vi and vii°. The key finder checks which keys contain the chords you entered, then weighs the evidence: the first and last chord, how often each chord appears, and strong signals like a V or V7 chord resolving to I.
Because a major key and its relative minor share the same chords, Am–F–C–G fits both C major and A minor. The finder shows both and ranks them. Your ear decides: which chord feels like home? If the progression keeps resolving to Am, the song is in A minor.
Clues that help
- The tonic chord is usually the first or last chord and feels like a point of rest.
- The dominant: a major V chord, often with a seventh (E7 in A minor), strongly points to its tonic.
- Raised notes in minor: in minor keys the V chord is often major because of the harmonic minor scale. E major in a progression with Am suggests A minor.
- Borrowed chords: a bVII (Bb in C major) or a iv (Fm in C) is common in pop and rock. They don't change the key, they add colour.
Related
Learn the theory behind this in diatonic harmony, key signatures and cadences. The interactive circle of fifths shows the chords of each key visually. To hear progressions in any key, use the progression player; to move a song to another key, the transposer. Browse all keys.