This music belongs to Portal 2 made by Valve. I own nothing.

Source: http://www.gamesradar.com/f/portal-2s-dynamic-music-an-interview-with-composer-mike-morasky-and-five-tracks-to-listen-to-now/a-201104121507877073
Also a BIG CREDIT to Dared00 for posting this link on Portal 2 forums.