The bad blood between Bungie and O'Donnell started when O'Donnell composed all of the music for the Destiny series up front, and publisher Activision chose to not release it as standalone pieces. Previous Halo soundtracks, music scored by O'Donnell, have all been released for purchase in the past, and have been featured heavily in those games' advertising and marketing. When Activision replaced the music for the game's debut E3 2013 trailer with something other than O'Donnell's, he was understandably miffed -- something that lead to where we are today. There's much, much more to this story and VentureBeat's write-up of the entire situation is incredibly comprehensive; you should definitely go check it out. If anything, this reveal clears up why Bungie's strangely been leaning so heavily on classic Led Zeppelin tracks for its TV spots.