Call of Duty: Advanced Warfare's new Exo Zombies mode has a secret. Anyone who finds it will be treated to a bonus song while they slay the undead.
Unlocking the song requires several steps. You have to find a saw, wrench, and bone saw and hold "X" while in front of them. This video from NoahJ456 (via Kotaku) shows the exact locations for each item:
As long as your teammates don't mind you putzing around while they fight off zombies, it should be easy enough to find these items. Once you've interacted with all three objects in any order, the music will begin. The song is "Ride of the Valkyries" by Richard Wagner. You've probably heard it (perhaps in Apocalypse Now) before even if you don't know the name. The music starts about 0:59 into the above video.
In Exo Zombies, four players must work together to fight off zombies that have overrun an Atlas facility. Unlike the zombies from previous COD games, these undead are equipped with exoskeletons so they're far more dangerous. Players won't start out with exo suits of their own but can find and upgrade them.
The survivors - voiced by John Malkovich and other celebrities - will earn money through killing zombies and can use it to buy upgrades and weapons. Zombies will drop power-ups as well in case players need that extra boost. Money can also be spent to open doors and advance through the map.
There's only one map, Outbreak, for Exo Zombies thus far. It was included with the Havoc DLC pack that launched on Xbox One and Xbox 360 on Tuesday. PlayStation platforms and the PC should receive this content sometime next month. The other three DLC packs planned for Advanced Warfare will presumably contribute new maps for the mode.
If you're intent on finding all the Easter eggs in Outbreak, be sure to check out NoahJ456's other videos. He's been poring over the map trying to find every little secret tucked away by Raven Software. For example, here's the bonus ending he uncovered: