Detect the musical key of any song, major or minor — for harmonic mixing, or making a sample sit in the same key as your track. Free.
The key finder identifies the musical key of a song — which note it centres on, and whether it's major or minor. It analyses which pitch classes actually appear across the track and how much weight each carries, then compares that profile against the characteristic shape of every major and minor key. It's the same approach a trained musician uses by ear, done arithmetically: the key whose expected profile best matches the song wins.
DJs use it for harmonic mixing, so a blend doesn't clash; producers use it to make sure a sample sits in the same key as the track it's going into. Songs that modulate, sit ambiguously between a relative major and minor, or lean heavily on chromatic material are the ones most likely to trip it up — the answer is a strong estimate, not a certainty. Beatmatching and key matching explained covers how to use it in a mix.
It analyzes the whole track's harmonic content: the audio is broken into short overlapping frames, each is transformed into a frequency spectrum, and the energy is folded into the 12 pitch classes (C, C♯, D … B) to build a chroma profile of which notes are most prominent. That profile is then matched against the classic Krumhansl–Schmuckler key templates for all 24 major and minor keys, and the best-correlating key wins. It's the same approach used by academic music-analysis tools, running entirely on your device.
On tonal, harmonically clear material — pop, rock, singer-songwriter, most electronic music — it's reliable. Accuracy drops on tracks that are ambiguous by nature: heavily atonal music, dense or distorted mixes, very percussive material with little pitched content, or songs that modulate between keys. The confidence score tells you how strongly the winning key stood out from the alternatives, so a low reading is a signal to double-check by ear.
It combines how well the track matched its best-fit key with how clearly that key beat the runner-up. A high score means one key fit distinctly better than all others; a low score means two or more keys fit almost equally well, which usually happens with ambiguous or modulating material. It's a guide to how much to trust the result, not a guarantee.
A major key and its relative minor (for example C major and A minor) use exactly the same seven notes, so from pitch content alone they can look nearly identical. The tool weighs where the tonal emphasis sits to choose between them, but on tracks without a strong tonal center it can pick the relative key. If the result feels off, the relative key (three semitones away) is the most likely correct alternative.
No. Decoding and the entire analysis happen locally in your browser — the file never leaves your device and nothing is sent to a server. You can confirm it by disconnecting from the internet after the page loads; the tool keeps working.