Some of the tracks referred to in this theory:
* Halo 1. Down In It
# Down In It (Skin)
* Halo 3. Head Like a Hole
# Head Like A Hole (Slate)
* Halo 17. And All That Could Have Been
# Terrible Lie
* Halo 18. The Hand That Feeds
# The Hand That Feeds
* Halo 19. With Teeth
# All The Love In The World
# You Know What You Are?
* Halo 20. Only
# Only
# The Hand That Feeds (DFA Mix)
# Love Is Not Enough (Live At Rehearsals)
# Only (Video) (??)
Supporters of this theory point to the following excerpt from the chat at the solutionsbackwardsinitiative website as suggesting there is a link between the materials with numbers on them and the music of NIN: