Music: Movement Proposition, Kevin MacLeod (incompetech.com)
Enable the 'Web Audio Input' experimental feature (chrome://flags/) and allow the web page to access your microphone when prompted.
Depending on your hardware, you may be able to get it to use your sound card's 'stereo mix' or 'what u hear' feature to use audio from other applications as input to the visualiser.
If not, you'll just have to sing into your microphone! ;-)
Unable to run this Web Audio API example. Check browser support