As with past installments of Call of Duty's co-op zombie slaughter downloadable content, the first episode of Advanced Warfare's Exo Zombies contains a hidden song. Unlike previous installments, this one's a bit more classy.
In case the famous John Charles Dollman illustration weren't clue enough, the song we're hunting for is Wagner's "Ride of the Valkyries", as made famous by the film Apocalypse Now. Nothing gets the blood pumping in the middle of a losing battle against the undead like those bombastic horns.
In order to unlock the musical Easter egg, three objects in the first Exo Zombies map must be touched.
The first is a wrench embedded in the wall of the Administration section.
The second is a Bone Saw, located on a table in the section off the left of the circular main hub.
Finally, at the top of the map in the Exo-Suit room, a Saw is hidden in a cracked open door.
Once you collect the third and final piece (in any order), the song begins to play.
I spent a couple hours yesterday attempting to activate this Easter Egg. Sadly the video I captured lacked sound, which is pretty important. Luckily YouTube's NoahJ456 posted his own video, with the song unlocking around the :56 spot