The mix
Bring in a song
A bounce, a zip of parts, or the demo.
Open Mix. Drop a file, or press Choose a file. A single song is the whole bounce. A zip of audio files becomes separate parts, named from the file names when the name is obvious (vocals, drums, bass, and so on).
The browser can read WAV, MP3, FLAC, and M4A. It turns them into WAV before they are stored. The server itself only decodes WAV.
Use the demo bounce when you want to learn the buttons without a song of your own. It is a short tone with parts already split, so you can press Make it sound finished and hear the path.
Nothing is sent to a GPU unless you ask, or this machine is too slow for the split. Bringing the song in stays on this computer.