How We Verify
Every key, tempo, and chord on this site falls into exactly one of three categories, always labeled: verified by ear, sourced from an academic dataset, or an honest gap. Nothing in between, and nothing guessed.
The rule: a gap is never filled with a guess
Automatic key detection is good enough to sound authoritative and wrong often enough to matter — in our own testing, the leading open audio-analysis tool (AcousticBrainz) got a song's key right only about 40% of the time. Publishing that as fact would make every song page a coin flip dressed up as data. So we don't. If a fact isn't verified, the page says so and offers to analyze the real track instead of printing a confident-sounding number.
Tier 1 — Verified by ear
A small set of flagship songs have every fact — key, chords, tempo, teaching notes — checked by ear against the actual recording. These pages carry a "✓ verified by ear" badge next to the key.
Tier 2 — The McGill Billboard Project
The bulk of the catalogue's key and chord data comes from the McGill Billboard Project, a CC0-licensed academic dataset built by McGill University's Distributed Digital Music Archives & Libraries Lab: expert human annotators — not software — logged the chords, tonic, and metre of Billboard Hot 100 songs from 1958–1991. It's the same kind of ground-truth data music-cognition researchers cite in peer-reviewed papers, not a scrape or a model's guess. Chord shapes rendered from it use real guitar fret/finger diagrams; ambiguous or unusual chord qualities (sus, dim, aug, and others our shape library can't render safely) are dropped rather than approximated.
Tempo
BPM comes from AcousticBrainz's DSP measurement of the actual audio — a real signal-processing analysis, not a classifier's guess — or a hand-verified reading for curated songs. Tempo estimation can land exactly double or half the true speed, so where that's a real possibility we publish both readings instead of silently picking one.
Everything else: genre, art, release year
Genre comes from MusicBrainz's crowd-voted artist tags (more specific than a flat "Rock"), with iTunes as a fallback. Album art, release year, and duration come from Apple's iTunes catalogue. None of these are music-theory claims, so the same verified/unverified split doesn't apply — but the same rule does: if a source doesn't have it, the field is left out rather than invented.
Frequently asked questions
Does Melody Monkey use AI to guess a song's key or chords?
No. A song's key only appears on its page if it was verified by ear against the actual recording, or comes from the McGill Billboard Project's expert human annotations. We tested automatic key-detection (AcousticBrainz) and found it right only about 40% of the time, so we never publish it — an unverified key shows as an "analyze it" link instead.
What is the McGill Billboard Project?
A CC0-licensed academic dataset of expert-annotated chords, key, and metre for Billboard Hot 100 songs from 1958–1991, built by McGill University's music research group. It's the source for the majority of Melody Monkey's chord and key data outside our hand-curated songs.
Where does the tempo (BPM) data come from?
From AcousticBrainz's DSP tempo analysis of the actual audio, which we've found reliable, or from a hand-verified reading for curated songs. Tempo detection can land an octave off, so where that's ambiguous we publish both readings rather than pick one.
What happens when a fact isn't verified?
It never gets filled in with a guess. A missing key, tempo, or chord list shows as a plain CTA to analyze the actual track — the gap is never hidden or quietly estimated.
See it verified yourself
Drop any track into Melody Monkey and get its real key, tempo, and chords analyzed from the actual audio — free, in about ten seconds.
Open the free app →