BPM & Key Finder — Song Key & Tempo Detector by Lacuna

Find the BPM, key, scale and Camelot code of any song — in seconds, without uploading it anywhere. Drop in an audio file and the entire analysis runs locally inside your browser. No account, no sign-up, no file ever leaves your computer.

Built for DJs planning harmonic sets, producers matching samples, and musicians who just need to know what key a track is in before they play along.

WHAT YOU GET
• BPM (tempo) — detected from the audio itself, not looked up in a database
• Musical key and scale — all 24 major and minor keys
• Camelot code — the number-and-letter wheel position for harmonic mixing
• A confidence score, so you know when a result is worth double-checking
• One-click copy for BPM and key results

WORKS WITH
MP3, WAV, FLAC, M4A, AAC, OGG — anything Firefox can decode. Drag a file onto the popup or click to browse.

WHY IT RUNS LOCALLY
Most BPM and key finders upload your track to a server. This one doesn't. The detection engine is compiled to WebAssembly and runs inside the extension, so unreleased demos, client work and anything else you'd rather not hand over stays on your machine. There is no backend to leak it and no account to create.

FREQUENTLY ASKED

How do I find the BPM of a song?
Drop the audio file onto the extension popup. The BPM appears in a couple of seconds, alongside the key, scale and Camelot code.

What is a Camelot code?
It's a shorthand for harmonic mixing — every key maps to a number plus A (minor) or B (major). Tracks whose codes sit next to each other on the wheel mix together without clashing. 8A and 8B are the same key in different modes; 8A and 9A are a step apart.

Can it detect the key of a song playing on YouTube or Spotify?
Not yet — this version analyses audio files you drop in, not tab audio. Download or export the track first, then drop it in.

Is it accurate?
It reports a confidence score with every result. Clean, tonal material scores high; heavily processed or atonal tracks score lower and are worth verifying by ear. That's true of every key detector, including the paid ones — this one just tells you.

Is it free?
Yes, and there's nothing to sign up for.