Methodology
Every number on this site comes from an engine you can check. This page documents how each one is measured — including what the tools can't do.
The ranges in the BPM Index are measured and hand-curated: typical tempo (the median of the genre in practice) plus the real range where productions actually sit. They are not scraped from an API — several popular sites still show data from Spotify's discontinued audio-features API; ours are maintained by a producer who works these genres.
Everything runs client-side in your browser: the audio is decoded and measured on your machine and never uploaded to any server. You can verify this in your browser's network tab.
Integrated loudness per ITU-R BS.1770-4: K-weighting filter, 400 ms blocks, absolute (-70 LUFS) and relative (-10 LU) gating. LRA per EBU R128 (10th–95th percentile of short-term loudness).
True peak (dBTP) with 4× oversampling using a windowed-sinc FIR interpolator, per ITU-R BS.1770-4 Annex 2. It is a real inter-sample peak, not the sample peak relabeled.
Autocorrelation over a spectral-flux novelty curve (50–200 BPM search range) with parabolic peak refinement and half/double-time disambiguation by energy.
12-bin chromagram correlated against Krumhansl-Schmuckler major/minor profiles, with relative-key disambiguation. The Camelot wheel position is derived from that result.
Platform verdicts compare your integrated LUFS against each service's normalization target (Spotify/YouTube -14, Apple -16, Deezer -15). Verdicts are always word + icon + color, with a color-blind-safe palette — color alone never carries the meaning.
When a measurement is an estimate, the UI says "estimated". We would rather tell you what the tool doesn't know.
Who measures
These tools are built and calibrated by a producer with 25 years of records — the same criteria used on real deliveries.