well I use royalty free music from : Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 3.0
Specific songs from that site:
Songs / titles:
Aftermath
Awkward Meeting
Bent and Broken
Birch Run
Darkest Child
Darkness is Coming
Devastation and Revenge
Dub Feral
Epic Unease
Ghostapocalypse - 1 Departure
Ghostapocalypse - 2 The Call
Ghostapocalypse - 3 Road of Trials
Ghostapocalypse - 4 Temptress
Interloper
Irregular
Lightless Dawn
Lithium
Lone Harvest
Martian Cowboy
Plaint
Private Reflection
Slow Burn
Spring Thaw
Static Motion
The Chamber
The House of Leaves
Thunder Dreams
What You Want ver 2
Wounded
I may add more to the list, There is simply to many songs on that site to go through all of them in one go.
I tried to choose music that had an “end days” feel to it.