Song Key Finder

Find out which key a song is in, for singing it, playing along, transposing it or mixing it with other tracks. The key finder listens to the whole song (up to 10 minutes), measures how much of each of the 12 pitch classes it contains, and compares that with the typical note pattern of every major and minor key. You get the key, its relative key, the Camelot code DJs use, a confidence rating and the runners-up. The audio never leaves your browser.

How to use this tool

1. Choose one or more songs.
2. Optionally set a start time to skip an intro.
3. Press Calculate and read the key, Camelot code and confidence.
4. If the confidence is low, look at the runners-up and check by playing the tonic chord along with the song.

Formula

r = correlation(chroma, key profile) for all 24 keys · key = the highest r

The song is decoded at 11,025 Hz in mono and cut into 4,096-sample windows (0.37 s, half overlapping). Each window's spectrum from 65 to 2,000 Hz is folded into 12 pitch classes (equal temperament, A = 440 Hz), scaled so its strongest class is 1, and added up. That chroma vector is compared (Pearson correlation) with the Krumhansl–Kessler major and minor profiles, which describe how strongly each scale step belongs to a key, rotated to all 12 tonics. Confidence is high when the best key correlates at 0.75 or more and leads the next by at least 0.1. Overtones of bass notes and the relative key's shared notes can mislead it, so treat a medium or low rating as a short list rather than an answer.

Example

A song built on the chords C, F, G and C (I–IV–V–I) is full of C, E, G, F, A, B and D, so its chroma matches C major best, clearly ahead of G major and A minor, the keys that share most of its notes. C major is 8B on the Camelot wheel and mixes well with 7B, 9B and its relative key A minor (8A).