In Reality Check you are actually playing as a player who got pulled into the world of Half Life 2 and now has to find his way through Improbability Zones, Combine Assaults, and even defeat the person that caused the improbability zones in the first place.
Nex_Varkhan, from Fur Affinity, gave their permission to use this music in the mod, Reality Check. To hear more of their music go to Furaffinity.net