Audio sources

Everything the visuals do starts with the sound. Choose a source from the Choose your music box when the app opens, or any time in the Audio tab under Source. The current source and a Play/Pause button sit at the top of that section; Space also plays and pauses (except in preview mode, where it fades).

The demo groove

A built-in house track at 124 BPM — kick, snare, hats, bass, pads and a lead melody, with a breakdown every 16 bars. It needs no permissions and no files, so it's the quickest way to try things out.

Audio files and folders

• Files… picks one or more audio files; Folder… picks a whole folder. You can also drag files or folders onto the page.
• Supported: MP3, WAV, OGG, FLAC, M4A, AAC and Opus (whatever your browser can decode).
• Several files become a playlist: it plays through in order, and you can jump to any track in the list.
• Drag the position slider to seek.

The beat grid

When a file starts, the whole track is analysed in the background — the status line under the source shows the progress. When it's done, the beat grid and any drops are known in advance, so transitions can land exactly on them (choose next drop as a transition's start, see Presets) and the beat holds steady through quiet passages. The result is remembered, so the same file is instant next time. Files up to 20 minutes are analysed; longer ones use live beat tracking.

Microphone and line-in

Microphone listens to the room — the browser asks for permission the first time. Pick a specific input (a USB interface, a mixer's line out) under Devices → Input.

The browser's echo cancellation, noise suppression and automatic gain are turned off, so the visuals hear the music as it is. If the visuals barely move, raise Input gain (this changes only what's analysed, not what you hear).

Play microphone through speakers sends the input to your speakers as well. Leave it off with a real microphone: it can feed back.

A browser tab, or the whole system

Tab audio (Chrome and Edge) captures sound from another tab: Spotify Web, YouTube, SoundCloud, a DJ stream. Your browser asks which tab to share — make sure sharing the tab's audio is ticked. On Windows, and on macOS 14.2 or later with recent Chrome, you can share the entire system's sound instead.

Spotify, Apple Music and other apps

If tab capture isn't available, install a free loopback audio device — BlackHole on macOS, VB-Cable on Windows. Send your music player's output to it, then choose it under Devices → Input. (There's a reminder of this in the Audio tab under Visualize Spotify, Apple Music or any app.)

Phones and tablets can only listen through the microphone.

Output device

In Chrome and Edge you can choose which speakers or interface the app plays to, under Devices → Output — handy for sending the music to a mixer while you monitor elsewhere.

Privacy

Audio is analysed on your own computer, in the browser, and never leaves it. Nothing is recorded unless you record a video yourself, and that file is saved straight to your device.