Song key finder
Type the chords of a song, or drop in an audio file, to find its key. Everything runs in your browser; files are never uploaded.
From chords
Recognised: AmFCGAmFCE
From an audio file
The first 90 seconds after the intro are analysed.
How key detection works
Every key favours certain notes: the tonic most, then the fifth and third, then the rest of the scale, with notes outside the scale rarest. In the 1980s psychologists Carol Krumhansl and Edward Kessler measured how well listeners felt each note “fit” a key, producing a profile for major and minor. Key finders count how often each note occurs in the music and pick the key whose profile correlates best.
The chord mode builds that note count from the chords you type (weighting the first and last chord a little more, since songs tend to start and end at home). The audio mode measures it directly from the sound. Once you know the key, use the chord transposer to move it, find its tempo with the BPM finder, or see it on the circle of fifths.
Questions
How do I find the key of a song?
Look at the chords: the key is usually the chord the song starts and ends on, and the one that feels like home. More reliably, count which notes the chords use and compare them with each key’s scale; that’s what this tool does.
How does the audio key finder work?
It decodes your file in the browser, measures how much energy falls on each of the 12 pitch classes (a chromagram), and correlates that profile with the Krumhansl–Kessler key profiles from music-perception research. Nothing is uploaded.
Why does it say C major when the song is A minor?
Relative keys share exactly the same notes, so they are hard to tell apart statistically. Check which chord feels like the resting point: if it’s Am, the song is in A minor.
How accurate is it?
For chord lists it is very reliable when you enter the whole song. For audio, clear tonal music works well; songs that modulate, use lots of borrowed chords or are mostly drums can confuse any key detector, so treat the top two results as candidates.