Song Key Finder
This song key finder listens to an audio file and tells you what key the song is in, with the chords and key signature that go with it.
Your file is analysed on this device and is never uploaded. MP3, WAV, M4A, OGG or FLAC, as your browser can read them.
Tap each note you hear in the tune (tap again to take it off). The keys that contain all of them are listed, most likely first.
Notes in the file
The chart shows how strong each of the 12 notes is in the file.
Key signature
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Chords in this key (tap to hear)
How to use the song key finder
This song key finder tells you what key a song is in: drop an audio file and it shows the most likely major or minor key, its relative key, the top three matches, the key signature and the chords of the key, or you can tap the notes you hear instead. Press Choose an audio file or drop a file on the box. The song key finder reads the notes in the first three minutes and shows the most likely key in large type, with its relative key under it. Your file is analysed on this device and is never uploaded.
Below the key you see the top 3 keys with a match score from 0 to 1. Tap any of them to see its details. The line above them also shows the tuning of the recording, in cents from A4 = 440 Hz, and says so when the top two are a close call.
Play tonic chord and Play scale let you check by ear: if the chord sounds like home when you play it over the song, you have the key. The chart shows how strong each of the 12 notes is in the file, with the notes of the key darker. On the right are the key signature and the seven chords of the key; tap a chord to hear it. For songs longer than about a minute you also get the key of each section.
No file? Choose Pick the notes you hear, tap the notes of the tune on the keyboard (tap again to remove one), and the tool lists every major and minor key that contains all of them, most likely first. Clear starts again.
How the key is detected
Like any music key finder, it has to turn sound into notes first. It lowers the sample rate to about 11 kHz and splits the sound into frames of about three quarters of a second. In each frame it finds the strong frequencies between 60 Hz and 2,100 Hz and works out which note each one is. First it measures how far the whole recording sits from standard tuning, so a song tuned a little sharp or flat still lands on the right notes. It then adds up how strong each of the 12 notes is across the file, which gives the chart.
That chart is compared with a profile for each of the 24 major and minor keys. The profiles come from listening tests by Carol Krumhansl and Edward Kessler, published in Psychological Review in 1982: listeners rated how well each of the 12 notes fit after a key was set up. The tonic scored highest in both, and the third and fifth came next. The key whose profile matches the file best (by correlation, the score you see) wins.
| Scale step | Major key rating | Minor key rating |
|---|---|---|
| Tonic | 6.35 | 6.33 |
| Minor 2nd | 2.23 | 2.68 |
| Major 2nd | 3.48 | 3.52 |
| Minor 3rd | 2.33 | 5.38 |
| Major 3rd | 4.38 | 2.60 |
| Perfect 4th | 4.09 | 3.53 |
| Augmented 4th | 2.52 | 2.54 |
| Perfect 5th | 5.19 | 4.75 |
| Minor 6th | 2.39 | 3.98 |
| Major 6th | 3.66 | 2.69 |
| Minor 7th | 2.29 | 3.34 |
| Major 7th | 2.88 | 3.17 |
The profile values are as listed in the music21 toolkit and by rnhart.net.
Why the answer can be a near miss
Automatic key detection is a best guess, not a fact about the song. Three mix-ups are common:
- Relative keys. G major and E minor use the same seven notes, so the note chart looks almost the same. The finder has to judge which note feels like home.
- Keys a fifth apart. G major and D major share six of their seven notes, and every note also sounds an overtone an octave and a fifth above it. In our tests on short loops this was the most common miss.
- Key changes. Many songs move up a step for the last chorus or change key in the bridge. One number cannot describe them, which is why longer files also get a key per section.
So check the top 3 by ear. Play the tonic chord of each while the song plays: the right one sounds settled, the others sound like they want to move.
Chords in a major and a minor key
Once you know the key, the chords that fit it follow a fixed pattern of major, minor and diminished chords on the seven scale steps. In a major key the pattern is I, ii, iii, IV, V, vi and vii° (capital numerals are major chords, small ones minor, and the circle means diminished). In a natural minor key it is i, ii°, III, iv, v, VI and VII. Minor songs often borrow a major V chord from the harmonic minor scale, which the tool shows as an extra chord.
To see how the keys connect, open the circle of fifths. To write a new part in the key you found, try the chord progression generator, and for the sharps and flats on the staff see key signatures.
Modes and songs without a clear key
The finder only chooses between major and minor keys. A song in a mode, such as Dorian or Mixolydian, will show as the major or minor key that shares its notes. Songs built on one repeated chord, drum-only tracks and heavily distorted guitars give weak note charts; the match scores will be low and close together, and your ears are the better judge.
Questions
What key is this song in?
Drop the file on the song key finder and read the key at the top. Then play the tonic chord along with the song: if it sounds like home, that is the key.
Is my audio file uploaded?
No. Your browser reads and analyses the file on your own device. Nothing is sent anywhere.
Why does it say the relative minor instead of the major key?
A major key and its relative minor share all seven notes. The finder weighs which note sounds like home, and it can pick the wrong one. The relative key is always shown right under the result.
What does the match score mean?
It is the correlation between the notes in your file and the profile of that key, from 0 (no match) to 1 (a perfect match). Scores close together mean the result is uncertain.
Can it find the key without a file?
Yes. Choose Pick the notes you hear, tap the notes of the tune on the keyboard, and the keys that contain all of them are listed.