Song key & BPM finder, in your browser.

Tip: for a beat you are about to sing over, run this first, then put the key in your prompt (“in F minor”) or pick the same key when you tune a vocal. Octa reads the key of its own beats automatically; this tool is for files that come from anywhere else.

Your browser decodes the file to raw audio and the page analyses the first three minutes at 22 kHz.

• Key. Short overlapping windows are turned into a spectrum; each spectral peak is folded to one of the twelve pitch classes to build a chroma profile. That profile is correlated with the Krumhansl–Kessler key profiles for all 24 major and minor keys. The best match is the key; the gap to the runner-up is the confidence.
• Tempo. The energy change between windows (onset strength) is auto-correlated; the strongest periodic pulse between 60 and 200 BPM is the tempo. Because half-time and double-time beats are both valid counts, the half and double are shown too.
• Camelot. The key is mapped to the 1A–12B wheel used for harmonic mixing.

Everything happens in JavaScript on your device. Close the tab and it is gone.

• Singing or rapping over a beat: know the key before you write the melody; if you tune a vocal afterwards, lock it to the same scale.
• Writing a prompt: add the key and tempo to a song prompt in the Octa studio when you want a track that sits with something you already have: “melodic trap in F minor, 140 bpm half-time”.
• Mixing two tracks: match Camelot codes (same code, one number apart, or same number with A/B swapped) and keep the tempos within a few percent.
• Covers and remixes: a different key from the original is a quick way to fit your range; a semitone up or down changes the Camelot code by seven positions.