Deadmau5 used to play around making music on Ustream, where he would let fans have a glimpse of how he produced tracks. The result left clips unreleased music floating around the internet.
A fan by the name of Ken had the idea to mix the clips from 2013 together, creating an amazing ambient Deadmau5 track. The end product is a progressive track with a chill buildup, with a drop that has Deadmau5's signature style. Check out incredible track below.
UPDATE:
@EDMsauce that was just a direct recording of a stream i did a while back tho, cool all the same. forgot about it!
— deadmau5 (@deadmau5) November 24, 2014