BPM and key finder

How it works

Tempo and key are the two numbers you need to mix tracks or build a set. The tempo comes from the rhythm: the detector measures how strongly new sounds start in every 6 ms slice of the track, then finds the beat period that repeats most strongly. The key comes from the harmony: each part of the spectrum that sits on a musical note is folded into one of the twelve pitch classes, and the resulting profile is compared with the classic Krumhansl–Kessler major and minor key profiles.

The key result is labelled as an estimate for a reason. Songs that move between relative keys (C major and A minor share every note), modal tracks and pieces with heavy distortion or no clear bass line can confuse any key detector, including the ones built into DJ software. When the match is weak the tool says “unclear” instead of guessing, and it always shows the runner-up key.

For mixing, the Camelot code is the useful part: keys with the same number (8A and 8B), or one step apart (8A, 7A, 9A), blend without clashing. See our guide to BPM for DJ mixing for how tempo and key work together.

Tips

• Same Camelot number, or ±1, mixes harmonically
• Check relative keys (e.g. A minor vs C major) by ear
• Analyse a full track, not a 10-second preview, for the best key estimate

Step by step

1. Open your audio. Click Open files or drop one or more MP3, WAV, M4A, OGG, FLAC or video files onto the page. They are decoded in your browser and never uploaded.
2. Read the tempo. The BPM appears with a confidence score and the top candidates. Use ½× or 2× if the result is half or double what you hear, or set a tempo range.
3. Check the beat grid. Click anywhere on the waveform to play from there with a click on every beat. Nudge the grid by 10 ms if it is slightly early or late.
4. Export. For several files, download the results table as CSV or TXT, or copy it to the clipboard.

FAQ