BPM and key finder: detect the tempo and key of any loop

Your file is decoded by your browser, then two detectors read it. The tempo comes from an open-source beat detector that finds the pulse in the first 90 seconds. The key comes from a chromagram: the audio is split into short frames, the energy at each frequency is folded onto the twelve notes of the scale, and that pattern is compared with the typical note patterns of all 24 major and minor keys.

Tempo can read half or double because a track really does sit at both. A trap loop at 140 has hi-hats running at that speed and a snare that lands once per bar, so it can feel like 70. The tool shows the half and double beside its answer so you can pick the one that matches how you count it. There is more on this in BPM by genre.

Treat the key as an estimate. It tells you which key the notes most resemble, not what the producer intended, and drums, 808s and loops that change chord can pull it off. A major key and its relative minor use the same seven notes, so they are the most common near-tie, which is why the result names the runner-up. Play the loop against a keyboard if it matters.