Audio Loop Analyzer
Load a loop or beat and the tool estimates its BPM, draws a beat & bar grid on the waveform, suggests bar lengths, and checks how cleanly the clip loops — all in your browser.
ℹ BPM detection is an estimate. It works best on steady, percussive material in 4/4; ambient, rubato, or tempo-changing audio can fool it. Tempo also has a built-in ×2 / ÷2 ambiguity — if the number looks doubled or halved, use the buttons, or just type the correct BPM (auto-detection covers 60–200 BPM; the field accepts 30–300). Nothing is uploaded; analysis runs on your device.
How It Works
Your file is decoded to raw samples in the browser. The tool measures a short-window energy envelope across the file and takes its positive changes to build an onset strength signal — spikes where new notes or drum hits begin. It then runs an autocorrelation on that onset signal: the lag where the signal best lines up with a delayed copy of itself is the beat period, and BPM = 60 ÷ beat period. A gentle preference curve around typical dance/pop tempos helps it pick the musically sensible octave. The beat grid is phase-aligned by sliding a pulse train until it best matches the onsets, and bar lines (every 4 beats) assume 4/4 time.
Because it’s based on energy, it shines on clear, steady beats and can struggle with sparse, ambient, swung, or tempo-changing music. The ×2 / ÷2 ambiguity is fundamental to tempo estimation — a backbeat can read as half or double the “real” tempo. If the grid doesn’t line up, nudge the BPM or use the octave buttons, then take the loop points into the Loop Audio Maker to cut a seamless loop.