Made with Processing.
It took quite a while for me to figure out how to get the audio data (e.g. FFT data) when it comes to render a video out of Processing (and the audio can't be played in real time). I finally found a clue in the Processing forums(processing.org/discourse/yabb2/YaBB.pl?num=1174169711/0), that the audio should be analysed in a separate sketch and the results are saved in a text file. These are the outputs I've got from three different Processing libraries (Minim, Sonia, Beads). You can also see that these libraries produces different data (e.g. length of the audio).
Rendered with Processing Video Library (MovieMaker).
Coldplay - Violet hill
Loading more stuff…
Hmm…it looks like things are taking a while to load. Try again?