Key and BPM Finder for any audio — find the key and tempo of your MP3 without guessing at it.
Upload a recording and ChordSonic reads the key straight from the sound: the tonic, and whether the track is major or minor. You get the chord progression it was read from on the same page, so the answer is something you can check rather than something you have to believe.
The key of the song, and the reason for it.
Most key finders hand back two words and leave you to trust them. Reading a key from audio is a judgement call — so this one shows its work.
- 01
The key
Tonic and mode
One label in the form musicians actually use — A minor, F♯ major, E♭ major. That is the note the music comes home to, plus the mode it sits in. It shows up beside the tempo on the result page and it is what the transpose control works from, so moving the whole chart into a key that suits your voice or your instrument is a click, not an exercise.
- 02
The chords behind it
Where the answer came from
The key is not read off a label buried in the file; it is worked out from the harmony the recording actually plays. You get that harmony too — the full chord progression, laid out along the timeline and lined up with the beat. A key nobody can check is a guess with confidence; a key with the chords underneath it is something you can scrub through and verify in about a minute.
- 03
Tempo and beat grid
Same upload, no extra step
The analysis reports the tempo in BPM and the beat grid in the same pass, because key and tempo are almost always wanted together — a DJ set, a sample hunt, a rehearsal chart. If tempo is the thing you came for, the BPM finder covers that side properly. Same upload either way.
From an MP3 to a key in about a minute.
No plugin, no install, no hunting for the root note on a keyboard. Three steps, in the browser.
- 01
Upload the audio
Drag in an MP3, WAV, M4A, MP4, FLAC or AIFF — up to 15 MB (25 MB with a free account). No account required to run it, and the file stays tied to you; nothing is public unless you choose to share the link.
- 02
The audio gets read
ChordSonic's pipeline pulls the mix apart, follows the harmony bar by bar, and builds the chord progression. The key falls out of that progression — which notes the music leans on, and for how long — rather than out of a raw guess at the file.
- 03
Read it and use it
The key appears beside the tempo, with the chord chart under it. Transpose the whole chart into a key that suits your voice, loop a section to check it by ear, or export the lot as TXT, CSV or JSON.
Honest limits.
A key is not written into an audio file anywhere. It is an interpretation of which notes and chords the music keeps returning to, and reasonable listeners disagree about it on real songs. So the number that matters is how often the read matches a human label, and it depends enormously on what is in the recording.
In our own testing against a held-out set of hand-labelled guitar recordings, the exact key came back right about three quarters of the time on takes with chordal accompaniment playing. On solo, largely single-note takes from the same library it landed under three in ten. That second figure is not a bug waiting to be fixed: a bare melodic line often does not contain enough harmonic information to fix a key at all, and no tool and no listener can recover what was never played.
When the read is wrong it is usually wrong in one of three recognisable ways: the relative key (C major against A minor — the same seven notes, a different centre of gravity), the same tonic in the wrong mode, or a neighbour a fifth away. All three are a glance at the chord chart away from being caught, which is exactly why the chart sits underneath the label instead of being hidden behind it. Dense mixes, heavy distortion and unaccompanied melodies are the hard cases; a clear arrangement with audible harmony is the easy one.
Take the result as a strong first read that saves you the searching, then confirm it with your ear the way you would confirm anything else you did not play yourself.
Four things worth knowing before you trust any key label.
Useful whether you use this tool or work it out by ear — these are the places where the question itself is slippery, not the answer.
Relative keys share every note
C major and A minor are built from the same seven notes; so are G major and E minor, and every other pair a minor third apart. Nothing in the note content separates them — only which chord the music treats as home. That is why a key finder and a musician can both be looking at the same song and name it differently without either being careless.
Parallel is not the same as relative
A major and A minor share a tonic but not a key signature; A minor and C major share a key signature but not a tonic. Mixing the two up is the classic theory slip, and it matters here because it is also one of the ways an automatic read goes wrong. If the label feels off, check whether the chords are pointing at the parallel mode rather than at a different note entirely.
Modal songs resist a single label
A lot of folk, rock and dance music sits in a mode — Dorian, Mixolydian — rather than in plain major or minor. Forced into a two-word answer, that comes out as the nearest major or minor key, which is useful for transposing and for picking a scale to solo over, but it is a simplification. The chord chart is where the modal colour is actually visible.
Not everything is tuned to concert pitch
Older recordings, tape, and bands who tuned down deliberately can sit measurably between two keys. The read snaps to the nearest one, which is the right answer for most uses and the wrong one if you are playing along at concert pitch and it will not quite line up. If your ear says the track is a fraction flat, trust your ear and tune to the record.
Who needs the key of a song, and what for.
Singers looking for a comfortable key
The recording sits too high for you, so you need to know where it starts before you can move it. Get the key from the audio, transpose the chord chart down by the interval that puts the top note back inside your range, and rehearse from the transposed chart instead of fighting the original all evening.
DJs mixing in key
Harmonic mixing needs the key of everything in the crate, and half a library usually arrives with that tag empty or wrong. Run the track, read the key and the tempo off the same result, and fill the tags in with something read from the audio rather than copied from a store listing.
Producers matching a sample
A loop that clashes with the rest of the session is normally a key problem, not a taste problem. Find the key of the sample and the key of the project, and you know exactly how far to pitch it — or whether to reach for a different loop before spending an hour on the one that will never sit.
Bands and worship teams building charts
Whoever writes the chart needs the key before anything else on the page makes sense. Pull it from the record, get the chord progression with it, transpose once for the whole band, and hand out something everyone can read instead of four people working it out separately in the car park.
Came for the key, need the tempo too?
One upload answers all of it, but each of these pages goes deeper on its own question.
BPM Finder
The tempo half of the same upload — beats per minute and the beat grid, from the audio.
Circle of Fifths
Once you know the key: its diatonic chords, its relative minor and its nearest neighbours, playable in the browser.
Guitar Chord Finder
The same analysis written for guitarists — chords, key and tempo out of a guitar recording.
Frequently asked
How do I find the key of a song from an MP3?
Upload the file. ChordSonic reads the recording, works out the chord progression, and reports the key that progression sits in — the tonic note plus whether the track is major or minor. You do not need to know any theory to use it, and you do not need to hunt for the root note on a keyboard. The answer arrives on the same page as the chord chart, so you can see what it was read from rather than taking a bare label on trust.
How reliable is the key detection?
Good on recordings with chords sounding through them, weak on sparse single-line playing, and we would rather say so than round it up. In our own testing against a held-out set of hand-labelled guitar recordings, the exact key came back right about three quarters of the time on takes with chordal accompaniment. On solo, largely single-note takes from the same library it was under three in ten. That is not a tuning problem waiting to be fixed: a bare melodic line frequently does not contain enough harmonic information to pin a key down, for any tool or any listener. Treat the result as a strong first read to check against your ear, not a verdict.
Why does it say A minor when I hear C major?
Because those two keys are built from exactly the same seven notes — they are relative keys, and telling them apart is a question of which note the music leans on, not which notes it uses. This is the single most common near miss, and it is often a genuine ambiguity in the recording rather than a mistake: plenty of songs really do sit between their relative major and minor. The chord chart on the result page settles it faster than any label can. If the progression keeps landing and resting on Am, read it as A minor; if it comes home to C, it is C major. The same applies to the other two near misses — the same tonic in the wrong mode, and a neighbour a fifth away.
Can it find the key of a song that changes key?
It reports one prevailing key for the upload — the one the track spends most of its length in. A last-chorus lift up a semitone, a bridge that borrows from the parallel minor, or a modulation halfway through will not appear as a second label. What does appear is the chord progression across the whole timeline, and a key change is usually obvious there: the chords stop belonging to the first key and start belonging to another. If you need a per-section answer, trim the file to the section you care about and run it again.
Does it find the key and the BPM together?
Yes. One upload returns the key, the tempo in BPM, the beat grid and the full chord progression — the analysis computes all of them in the same pass, so there is nothing extra to run and nothing extra to pay. If tempo is the thing you actually came for, the BPM finder page covers that side in detail, but the upload is the same upload and the result page is the same page.
What files can I upload, and do I need an account?
No account needed to run it. We accept MP3, WAV, M4A, MP4, FLAC and AIFF. Up to 15 MB and 5 minutes without an account, or 25 MB and 8 minutes with a free one. Most single songs fit comfortably. If yours does not, trim it — a chorus and a verse are plenty for a key read, and a shorter clip comes back faster.
Can it find the key of a track from YouTube?
Not from a link — we need an audio file. Download the audio legally (your own purchase, a Bandcamp download, a creator's official file), then upload it here. Recordings pulled from video are usually fine as long as the audio is not drowned in speech or crowd noise; the harmony has to be audible for anything to read it.
Find the key of your track from the audio.
Drop in an MP3 or WAV and get the key, the chords it was read from, and the tempo on one page. Up to 15 MB and 5 minutes without an account, or 25 MB and 8 minutes with a free one. Free, no credit card.
Want the notes that go with it? Every major and minor scale is written out here, modes and pentatonics included.
Mixing in key? Once you have the key, the Camelot wheel translates it into a mixing code and shows you which codes sit next to it.