Tempo mapping

Build a tempo map from the audio

This tool writes a first-pass tempo map from the audio. Some songs come out clean, some don’t, and you’ll see which in seconds. Keep the map, tweak it, or throw it away and start from scratch.

  • All processing happens on your computer. Your audio file and chart are never uploaded to a server.
  • The first run downloads about 515 MB of model files.
  • Needs WebGPU, so a recent Chrome or Edge.

Above: a generated tempo map can land off the beat. Drag a beat or bar line in the editor to line it up with the notes.

Start a song

Pick a song file to get a new chart holding just the tempo map, or an existing chart to rebuild its tempo map without moving its notes in the audio.

Builds a tempo map and beat grid in your browser. Start from a song file to get a fresh chart, or from an existing chart to rebuild its tempo map without moving any notes.

Everything runs on your computer. Nothing is uploaded. The first run downloads about 515 MB of models: the drum separator, the beat tracker, and the transcription model whose drum hits the map is fitted to.

When it works, and when it doesn't

A song that stays in 4/4 usually gets a map you can work with, even when the tempo speeds up, slows down, or drifts. A song that changes meter or sits in odd time should be tempo mapped by hand.

How it scores

Each generated tempo map was checked against the tempo map in the original chart.
Tempo-map measurements for this tool and ConvertHero on 367 songs.
MeasurementThis toolConvertHero
Average tempo error (lower is better)10.1%21.4%
Drum hits within 15 ms of a grid line (higher is better)81.4%66.6%
Downbeats correctly identified within 30 ms51.0%Not detected

ConvertHero is an open-source automatic chart tempo-mapping tool.

Tested once on 367 songs by comparing each generated tempo map with the tempo map in the original chart. Of those songs, 223 (60.8%) contain only 4/4 time signatures. ConvertHero receives its best result from the tested settings on each scored row. Confidence intervals have not been calculated.

What it does

Three models run on your machine: one separates the drums out of the mix, one finds the beats, one finds where the drum hits land so the map can be pulled onto them. What comes out is a first pass at the tempo map, and the last step is where you take over.
  1. Separate the drumsBS-Roformer, a separation model, isolates the drum stem from the full mix.
  2. Find the beatsBeat This!, a beat-tracking model, listens to the full mix and to the drum stem and marks where the beats and the bar starts are.
  3. Fit the tempo mapA postprocessing step tuned for charts converts the grid into a tempo map.
  4. Check it against the audioThe map opens on a timeline over the waveform. You play it back, move markers or bar lines, and export a .zip or .sng.