Song Analyzer

A BPM and key finder in one pass

Analyze any song's BPM and key in one upload — a combined BPM and key finder that also reports loudness and spectrum. Instead of running two tools and uploading the file twice, the analyzer chains its tempo, key, loudness, and spectrum passes in a single run and hands you one report card. DJs get the BPM and Camelot code they need for harmonic mixing; producers get the loudness numbers; everyone gets the answer in seconds, without the file ever leaving the browser.

What does a song analyzer measure?

• BPM — the tempo, from an energy-envelope autocorrelation pass.
• Key — estimated with the Krumhansl-Schmuckler algorithm, with the Camelot code for DJing.
• Loudness — integrated LUFS (K-weighted, ITU-R BS.1770 style) plus true peak and RMS.
• Spectrum — average energy across 64 log-spaced frequency bands, and the low/mid/high split.

BPM, key, and energy: reading the numbers

BPM tells you the rhythm; key tells you the tonal home; the loudness figure tells you how hard the master is pushed. Streaming platforms normalize around -14 LUFS, so a track measuring -8 LUFS is loudness-war territory and will be turned down; one at -20 LUFS is dynamic and will be raised. The low/mid/high split is a quick mix-balance check: a club track usually shows a heavy low end, an acoustic ballad a mid-focused profile.

Using analysis for DJing and production

For DJs: export the JSON, note BPM and Camelot codes, and build playlists that mix harmonically at compatible tempos. For producers: use loudness and spectrum numbers as reference checks when comparing your mix to commercial tracks. For teachers and transcribers: BPM and key give you the scaffolding before you write a single note.