Chord, Key & Tempo Detection

Treat every field as an estimate, and the page says so under the results. The key comes from correlating the track's pitch-class profile against the standard Krumhansl–Schmuckler major and minor templates: it is dependable at finding the tonal centre on clearly tonal music, and its classic failure is confusing a key with its relative major or minor. Tempo is beat-tracked, so it can land on half or double the tempo you'd count. Modulating, rubato, atonal or very percussive tracks are the hard cases.

It is a rough harmonic sketch, not a transcription. Chords are matched window by window against 24 templates — twelve major triads and twelve minor ones — so sevenths, suspensions, diminished and augmented chords, slash chords and inversions all get flattened to the nearest plain triad. It is useful for finding the progression to jam over; it is not a lead sheet.

The time signature is a two-way decision between 3/4 and 4/4, made by checking which grouping gives the strongest downbeat contrast — 6/8 material comes out as 3/4, which matches how most people count it, and nothing more exotic is detected. Sections are structural boundaries estimated from the audio and are used to populate the practice loop; short tracks may not split into sections at all.

Audio or video files up to 100 MB and 30 minutes. Analysis is free — no credits — but you need to be signed in, and it is limited to 20 analyses a minute. Your upload is deleted from the server once the analysis returns. The practice loop below the results plays the file straight from your browser without re-uploading it, so you can slow a section to half speed with the pitch preserved.