Detect Song Key + BPM — Offline
Drop a track into MiniMax Converter's Mix screen, click Analyse keys, and every song in the playlist gets its detected key (e.g. C, F#m, Am) plus a 20-character mini-waveform with a scrolling playback cursor. The Pitch / Tempo screen also detects BPM and uses it to centre the tempo slider on the song's actual beat — handy for DJs, samplers, anyone matching tracks.
How key detection works
The app uses the Krumhansl-Schmuckler algorithm — the academic-standard approach. It extracts a chroma vector from the first 90 seconds of audio (FFT into 12 pitch classes), then correlates against the 24 major + minor key profiles. Best correlation wins. Pure Python + numpy, no external service.
How BPM detection works
Spectral-flux onset envelope + autocorrelation. The app builds a frame-by-frame measure of where energy in the spectrum jumps, then autocorrelates that signal to find its dominant period. Good for ~80% of percussive music within ±1 BPM; struggles on ambient / free-time material.
How to use it
- Drop one or more audio files onto the Mix screen.
- Click Analyse keys in the toolbar. Each song gets its key + waveform appended to the row (background job; progress visible).
- For BPM, open the Pitch / Tempo screen and click Analyse. The tempo slider re-centres on the detected BPM.
Questions and answers
How accurate is the key detection?
Roughly 70–80% within the correct key on tonal pop / rock / folk material. It can land a perfect fifth off on ambiguous tracks; a manual override dropdown lets you correct it.
Does it detect modes (Dorian, Mixolydian, …)?
No — only major and minor. Modal music gets classified as the closest of the two.
Can I batch-analyse a whole folder?
Yes. Drop a folder onto the Mix screen and every supported audio file is imported. One click on Analyse keys processes the whole playlist in the background.
Why offline?
No upload limits, no API fees, no privacy concerns — your music never leaves your machine.
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Get MiniMax Converter
Cross-platform desktop app. Linux free for non-commercial use; Windows & macOS one-time €20 license. No subscription, no telemetry, no account.