How accurate is automatic key detection?

On clearly tonal music — most pop, rock, dance and folk — it is right most of the time, and when it is wrong it usually names the relative major or minor rather than something unrelated. It gets much less reliable on modal music, jazz, anything that modulates, and tracks that are largely percussion. That is why a confidence score is shown: treat a low one as the tool telling you the question does not have a clean answer.

What is the difference between this and a song key database?

A database looks up a title and returns what was recorded for that release; it cannot help with your own file, and it can be wrong about remixes and alternate versions. This analyses the audio you actually have. For a well-known single, either works. For anything else, only this one does.

Why does it say C major when the song sounds like A minor?

They contain exactly the same notes — the only difference is which one feels like home, and that is a matter of emphasis rather than pitch content. Automatic detectors work from pitch content, so this pair is the hardest distinction to make. Both are shown for that reason. Trust your ear over the label here.

Is this key detector free, and do I need an account?

Free, and no. There is no sign-in, no credit cost and no cap on how many files you run — the analysis happens in your own browser, so it costs us nothing per use.

Is my file uploaded anywhere?

No. The file is decoded and analysed inside this page and never transmitted. That is worth knowing if you are checking an unreleased track.

Can it find the key of a YouTube or Spotify track?

Not directly — it needs an audio file on your device, and downloading from either platform is against their terms. If you have the file legitimately, it works on it like anything else.

Does it detect the key of a song with a key change?

It returns one key for the whole file — whichever dominates — and the confidence score drops, which is the signal that something is going on. If you need the key of a specific passage, cut that section out first with the audio cutter and analyse just that.

What do the twelve bars underneath the answer mean?

That is the chroma profile: how much energy the track spends on each of the twelve note names across its whole length. The tall bars are the notes the song is built from. It is the evidence behind the answer, and it is often more informative than the label — you can usually see the key in it yourself.

Does it show BPM as well?

Yes, from the same analysis. If tempo is the main thing you are after, the BPM finder page runs the identical measurement with the tempo leading, and covers the half-time and double-time question properly.

Which files can I use?

Anything your browser can decode: MP3, WAV, FLAC, M4A, AAC, OGG, and the audio inside video files. Longer files just take a little longer; the practical limit is about 100MB.

Rewave

Song Key Finder

Analyse any audio file and get the key, the relative major or minor, and the BPM — with a confidence score, so you know when to trust it. Nothing is uploaded.

Key + BPM together
Confidence score, not just a guess
Free, no sign-in
Nothing is uploaded

What it does

The key of the file, not the key in a database

Most song key finders are lookup services: you type a title, they return what someone recorded about that release. That works for a chart hit and fails for everything else — your own demo, an unreleased edit, a live version, a track a friend sent you, a stem you just bounced.

This reads the audio instead. Every moment of the file is broken into frequencies, each frequency is folded onto one of the twelve note names, and the resulting profile is matched against all twenty-four major and minor keys. What comes back is the closest match plus a number saying how close it was.

That confidence number matters more than people expect. Plenty of music does not have one key — it modulates, it is modal, it is mostly drums — and any tool that answers with a flat "F♯ minor" and no caveat is hiding that from you. The tempo is measured in the same pass, since anyone asking about the key usually wants the BPM too.

A piano keyboard photographed from directly above, keys running off both edges

How it works

How to find the key of a song

One file, a couple of seconds, no account.

1
Choose the audio file
MP3, WAV, FLAC, M4A, or a video file. It is read by your browser and stays on your device.
2
The pitch content is measured
The whole track is analysed, not a sample of it, and the energy on each of the twelve note names is totalled up.
3
Read the key, the relative, and the BPM
You get the best-matching key, its relative major or minor, a confidence score and the tempo — plus the note-by-note chart the answer came from.

What you get

What a music key detector should tell you

The key, and how sure it is

A single key name with no confidence attached is a guess dressed up as a fact. When the score is low, that is real information about the music — usually that it does not sit in one key.

Four chords, one keyreliable

Modal, no clear tonicread the confidence

Key change halfwayread the confidence

Drum-only introread the confidence

The relative major or minor, side by side

C major and A minor use exactly the same seven notes, so every automatic detector can confuse them. When the answer feels wrong, it is almost always the relative — so both are shown rather than one being hidden.

C major

A minor

G major

E minor

F major

D minor

D major

B minor

A song key and BPM finder in one pass

The tempo comes out of the same analysis, so you do not need a second tool. If it is the beat you came for, the BPM finder puts that first instead.

Every frameis split into frequencies

Each frequencyis folded onto one of 12 notes

The 12 totalsare matched against all 24 keys

The best matchis the key, with a confidence score

Works on files no lookup site has

Because it analyses the audio rather than searching a catalogue, your own bounce works exactly as well as a released single — and the file never leaves your browser.

lookup sites

search by title
only released tracks
nothing for your own demo

here

analyses the actual file
any audio you have
never leaves your device

Who uses it

When you need the key

Harmonic mixing

DJs match keys so two tracks do not clash. Knowing the key of every record in a set is the whole basis of it.

Writing over a sample

Before you can add a bassline you need to know where home is. The key tells you which notes will sit right.

Picking a cover key

Find the original key, then decide how far to transpose it for the voice actually singing it.

Choosing a backing track

A jam track only helps if it is in the key you are practising. Check before you commit an hour to it.

Cataloguing your own library

Run your bounces through and tag them, so future-you does not have to work it out again by ear.

Checking your ear

Guess first, then analyse. Disagreements are the interesting ones — often the track is genuinely ambiguous.

FAQ

Song key finder questions

More tools

Other Rewave AI music tools

Find the key

Drop in a file and get the key, the relative and the tempo. Nothing uploaded.

Or generate a new song