BPM and Key Finder
Drop in a track and get both readings at once. No signup, no upload, no limit.
Got the tempo and the key? Melodious turns the whole track into a music video — See how
Drop an audio file to get its BPM and key
MP3, WAV, M4A, FLAC or OGG
Your file never leaves your browser — both readings are computed on your device and nothing is uploaded.
How to find a song's BPM and key
To find a song's BPM and key together, drop the audio file onto the tool above. It reads the file once and runs two separate analyses on it: the tempo comes from the spacing of the track's onsets, and the key from which of the twelve notes the music actually uses. Both answers appear together in a few seconds, each with its own confidence rating. Nothing is uploaded — the file is decoded and analysed on your own device, so the tool works offline and needs no account. The two readings are independent: a track can have a rock-solid tempo and an ambiguous key, or the reverse, which is why they are rated separately rather than blended into one score.
Why the two readings fail independently
Tempo and key are measured from different properties of the same audio, and knowing which one to distrust on a given track is most of the skill in using a tool like this.
Tempo comes from onsets — the moments where the signal jumps, which on most records means drums. So the tempo reading is strongest exactly where the key reading is weakest: a loud, percussive, rhythmically rigid track. Give it a solo piano ballad played with rubato and it has almost nothing to lock onto.
Key comes from pitch content — how much energy sits on each of the twelve notes across the whole track. That needs sustained, tuned material. A drum loop has none, so it returns no key at all rather than inventing one. The ambient pad that defeated the tempo detector gives a clean, confident key.
This is why the two confidences are shown separately. A single blended score would let a confident tempo mask an unusable key, which is precisely the error that costs you an afternoon when you transpose a session onto the wrong reading.
Using the pair: harmonic mixing
The main reason to want both numbers together is matching one record to another. Tempo alone is not enough — two tracks at the same BPM in clashing keys sound worse mixed than either does alone, and the clash is more obvious than a small tempo drift.
Keys that share most of their notes blend cleanly. In practice that means moving to the relative major or minor (A minor from C major — the same seven notes), or up or down a fifth (C major to G major, one note different). Those three moves cover most of what DJs mean by a compatible transition, and they are why Camelot and Open Key wheels are laid out the way they are: adjacent positions on the wheel are exactly these relationships.
The tempo side is simpler and more forgiving. Anything within a few BPM will pull into line without audible artefacts. Beyond roughly six per cent, time-stretching starts to be something the listener can hear on vocals and cymbals.
When the tool disagrees with your ear
Your ear wins. That is not modesty — it is the correct rule. Both methods here measure statistical properties of a recording, and both have known blind spots the page is explicit about: half and double tempo are the same pattern to a beat detector, and relative major and minor are the same seven notes to a key detector.
The tool's job is to be right often enough to save you the work, and to say so clearly when it is unsure. When it flags a close call, spend the ten seconds: count the beats over four bars, or hum the note the song settles on at the end of a phrase. Both settle the question faster than any amount of extra computation.
Frequently asked questions
How do I find the BPM and key of a song?
Drop the audio file onto the tool on this page. It decodes the file once and runs both analyses on it, returning the tempo and the key together with a confidence rating for each. No account, no upload, no limit — the whole thing runs in your browser.
Why do I need both numbers?
Because most of the jobs that need one need the other. Mixing two records together requires their tempos to match and their keys to be compatible, or the transition clashes. Picking an acapella or a sample to lay over a beat needs the same pair. Choosing a backing track to sing over means matching the key to your range and the tempo to the feel. In each case one number on its own only gets you halfway.
Is it free, and does my music get uploaded?
Free, no account, no limit, and nothing is uploaded. Your browser decodes the file and analyses it on your device. You can verify that by watching the network tab while you use it, or by disconnecting from the internet after the page loads — it still works.
Can the tempo be right and the key wrong, or the other way round?
Yes, and it is common. They are measured from completely different properties of the audio. A drum-heavy track with almost no harmonic content gives a confident tempo and no usable key at all. A slow ambient pad is the reverse: the key is clear and there is no beat to lock onto. That is why each reading carries its own confidence rather than the page reporting one blended number that would hide both failure modes.
The key is a semitone or a whole step off from what I expected.
Check whether the recording is pitched. Records mastered from tape, sped-up or slowed-down edits, and anything transposed for a vocalist will read at their actual pitch rather than their nominal one — the tool measures the audio, not the sheet music. If the reading is a relative major or minor away instead, that is the harder and more common ambiguity, and the tool flags it when the call was close.
The tempo came out at half or double what I hear.
Beat detection genuinely cannot distinguish a bar from a half-bar from audio alone — 140 and 70 are the same pattern at two readings. The detector corrects the common case by doubling anything below 80 BPM, because very little popular music sits there. If the number still looks halved or doubled, it almost certainly is, and the fix is to trust your count.
What audio formats work?
MP3, WAV, M4A, FLAC and OGG generally work. Decoding is handled by your browser, so support varies slightly between Chrome, Safari and Firefox. If a file is refused, converting it to WAV or MP3 fixes it.
You have the tempo and the key. Want the video?
Attach a track and describe what you want in one message. An AI director storyboards it scene by scene, with the same character in every shot. Your first project's keyframes are free, so you see the whole storyboard before deciding to render.
Start your videoLooking for just one of them? BPM finder · Song key finder · Tap tempo · AI music video generator