Audio nerd lab
For example, you can plug in audio effects on music that is streaming. Or, as I did in this case, have an analyzer listen to your music.
If you click the speaker icon above, the song ‘Albnd Zwecks‘ by Olaf Wempe will start to play. WebAudio analyzes it as it plays, and returns a bunch of numbers that I can use to animate the scene in real time.