This is quite cunning, it appears to have the FFT pre-parsed as JS objects. It then actually plays back a single audio file (http://daftpunk.themaninblue.com/Cameron%20Adams%20-%20Defin... or ogg version), while using the js object data to represent the FFT data. e.g http://daftpunk.themaninblue.com/js/data_da_funk.js

A very convincing illusion of a 'realtime' mashup, but the audio API spec just isn't there cross browser to allow this in real time right now.