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Key & BPM Finder

Get the key, Camelot code and BPM for a track in seconds. Queue up several files to build a table, then export it as CSV — analysis stays on your device.

Drop a track here to detect key and tempo

or browse for a file on your device

MP3 · WAV · FLAC · AAC · M4A · MP4 · OGG · OPUS · 25 MB max

Nothing leaves your device

Decoding, measurement and export all happen locally, using your browser's own audio engine. Your file never reaches our servers, and closing the tab clears it from memory.

  • No cost
  • No sign-up
  • Runs on-device

The method behind the numbers

Tempo is derived from a spectral-flux onset envelope, which tracks how sharply energy rises between successive short-time spectra and produces a spiky signal that peaks at note and drum attacks. Autocorrelating that envelope exposes the underlying pulse, and the strongest peak within a musically plausible range becomes the BPM estimate.

Key is derived from a chromagram: each frequency bin is folded into one of twelve pitch classes, weighted by energy and averaged across the track to build a fingerprint of how heavily each note is used. That fingerprint is then correlated against the Krumhansl-Schmuckler profiles for all 24 keys, yielding both the best match and a measure of how decisively it beats the alternatives.

Both techniques are decades old, well documented, and intentionally not a black box. Where the method struggles, the confidence score reflects that honestly instead of dressing up a weak result as a certain one.

Putting key and tempo to work in a DJ set

Harmonic mixing means picking the next record so its key sits comfortably against whatever is already playing. Camelot codes make the rule easy to apply: stay on the same number, step one number up or down, or swap the letter while keeping the number. 8A works into 8B, 9A or 7A; jumping to 3B does not.

Tempo matters just as much as key. Modern time-stretching hides a four to six percent tempo shift almost completely, but push beyond that and you either shift the pitch — undoing your key planning — or start hearing artefacts. Sorting a crate by BPM alongside Camelot code is the quickest route to a set that flows.

  • Same Camelot code: a perfect harmonic match
  • ±1 on the wheel: the standard smooth transition
  • Same number, different letter: relative major/minor, an easy mood change
  • +7 on the wheel: an energy lift, use sparingly

When to be skeptical of the result

Key detection assumes the track stays in one key throughout. Anything that modulates, borrows from parallel modes, or leans on chromatic harmony will return a low-confidence answer that's best treated as a hint rather than a fact. Drum-only material, sound design, and heavily atonal tracks have no real key at all, so the output there is just noise dressed up as a number.

Tempo detection assumes a steady pulse. A live take with rubato, a ritardando, or a drummer who drifts will produce an average rather than a true grid. And if a track opens with an intro at a different feel, whichever section runs longer ends up dominating the estimate.

Common questions

  • It builds a chromagram — the amount of energy in each of the twelve pitch classes across the entire recording — and compares that profile against the Krumhansl-Schmuckler key profiles for all 24 major and minor keys. Whichever key correlates best wins, and how far ahead it is of the runner-up becomes the confidence figure.

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