Find the key of a song from the audio file
The Key Finder listens to a song file and tells you its musical key — for example A minor or E♭ major — together with the Camelot code DJs use for harmonic mixing, the relative key, a confidence rating and the runner-up keys. Drop in one track or a whole folder: every file is analysed in turn and the results can be downloaded as a CSV for your music library.
Musicians use it before learning a cover, singers to check whether a song suits their range, producers to match a sample to a project, and DJs to plan mixes that do not clash. It also estimates the tuning (A4 = 432 Hz shows up clearly) and checks the song section by section for key changes.
Everything happens in your browser. The audio is decoded and analysed on your own device; no file is uploaded.
How to use the Key Finder
- Drop one or more audio files onto the box (MP3, WAV, M4A, OGG, Opus or FLAC), or click it to choose them.
- Wait a few seconds per song while the progress bar runs — press Cancel to stop a long batch.
- Read the key, Camelot code, relative key and confidence. Check the Runner-up keys table if the confidence is not high.
- Look at Key by section for modulations, and play the track to see the chromagram follow along.
- For a batch, use Show to open any song, then Download CSV to save every result.
Key Finder features
Two proven key profiles
The song’s note profile is matched against the Krumhansl–Kessler and Temperley profiles for all 24 keys, or their average.
Camelot wheel
The detected key is highlighted on a Camelot wheel with its compatible neighbours.
Confidence and runner-ups
A rating from the strength of the match and its lead over the next key, plus the five closest alternatives and how they relate.
Tuning estimate
The reference pitch (A4 in hertz and cents) is measured and compensated before the key is named.
Key changes
Longer songs are split into sections of 6–30 seconds and each section gets its own key, revealing modulations such as a final chorus a step higher.
Batch and CSV
Analyse many files in one go and export every result to a spreadsheet.
How the key is detected
The audio is mixed to mono and resampled to about 11 kHz. A Fourier transform of each 0.7-second slice finds the strongest spectral peaks between 60 Hz and 2.1 kHz — the range of bass lines, chords and melodies. Each peak’s exact frequency is converted to a note, and its strength is added to one of the 12 pitch classes (C, C♯, D … B). The average deviation of all peaks from equal-tempered pitch gives the tuning estimate, which is removed before the notes are counted.
The result is a 12-number pitch-class profile of the whole song, compared with the expected profile of each of the 24 keys using Pearson correlation; the best match is the key. The Krumhansl–Kessler profile comes from listening experiments, Temperley’s from note counts in textbook excerpts. Both rank the tonic, fifth and third highest.
Camelot codes and harmonic mixing
The Camelot system numbers the 24 keys like a clock: majors are 1B–12B and minors 1A–12A, arranged so that neighbours are a fifth apart. Tracks mix smoothly when their codes are the same, one number apart in the same letter (for example 8A → 9A), or the same number with the other letter (8A ↔ 8B, the relative major/minor pair).
| Camelot | Major (B) | Minor (A) |
|---|---|---|
| 1 | B major | A♭ (G♯) minor |
| 2 | F♯ major | E♭ (D♯) minor |
| 3 | D♭ major | B♭ minor |
| 4 | A♭ major | F minor |
| 5 | E♭ major | C minor |
| 6 | B♭ major | G minor |
| 7 | F major | D minor |
| 8 | C major | A minor |
| 9 | G major | E minor |
| 10 | D major | B minor |
| 11 | A major | F♯ minor |
| 12 | E major | C♯ minor |
How accurate is automatic key detection?
On music with clear harmony — most pop, rock, folk, classical and dance tracks — the profile method agrees with the published key on most songs. Its typical mistakes are musically close: the relative key (C major vs A minor share the same notes), the key a fifth away, or the parallel key (C major vs C minor). That is why the runner-up keys are listed and why a low confidence rating deserves a second look.
It struggles with modal music (Dorian, Mixolydian), blues built on dominant-seventh chords, atonal or heavily distorted tracks, rap and drum-only passages with little pitched sound, and songs that change key often. Confirm by ear: hum the note that feels like “home”, or check it against an instrument or the Online Tuner. Pair the key with the tempo from the BPM Detector to build a complete DJ crate, or move a song to a different key with the Audio Pitch Changer.
Key Finder FAQ
How do I find the key of a song?
Drop the audio file onto the key finder. In a few seconds it shows the key, for example “G major”, with its Camelot code, relative key and confidence.
Is this key finder free and private?
Yes. It is free with no sign-up, and songs are analysed on your device — nothing is uploaded.
Why does it say A minor when the song is in C major?
C major and A minor use exactly the same seven notes, so their profiles are very similar. The tool decides from which notes are emphasised; if the runner-up is the relative key with a close score, listen for which chord feels like the resting point.
What does the Camelot code mean?
It is a DJ-friendly label for the key: a number from 1 to 12 and a letter, B for major and A for minor. Songs with the same number, or numbers next to each other with the same letter, mix together without clashing.
Can it detect key changes?
Songs longer than about 12 seconds are analysed section by section. If a different key holds for a section, the change is listed with its time — useful for spotting a final chorus that moves up a step.
What tuning does the result assume?
None — the tool measures it. If the recording is tuned to A4 = 432 Hz or is a little sharp or flat, the offset is shown in hertz and cents and corrected before the key is chosen.
Can I analyse a whole playlist?
Yes. Drop many files at once; they are processed one after another, and Download CSV saves all the results.