To hear 'I'm Not Ready to Die' by Avenged Sevenfold on the Call of the Dead Zombie level, follow the instructions below:
You need to find and use the three meteorites on this level.
To get the first one, you should look in the opening area, to the left of where you start.
The second one is through the right-hand 750 points door looking towards the lake. Head upstairs, into a room with some tables where you can find the meteorite on a chair.
The final one is through the 750 point path to the left of the starting area. At the lighthouse, go right and downstairs into a room. The meteorite is near the light on the floor. You will then hear 'I'm Not Ready to Die' by Avenged Sevenfold.