The track lists are not following the actual level structures of Black Edition and Overdose - and you wonder why? Let me tell you all how it is.

If you look in the music folder, the Cathedral was supposed to be the first place you go to, but it switched places over to the Cemetery, for some reason.

The levels and the music in PK Overdose is internally ordered in a completely different way compared to the chapters and level structure the game follows. If you take a look, it's ordered entirely differently compared to the chapters of the game. It's not explained anywhere (not even TCRF has a page about it), but I believe that the levels and chapters were supposed to be structured exactly how the internal structure would suggest. The Cataclysm is the first level of the game, but originally, it's internal name and the track for it shows that it would be a entirely different level in a different chapter ( Chapter 2 or if you really want to be internal, Chapter 8.), and it would follow Dead Marsh, (which for some reason uses the tracks meant for the Cataclysm), not Japanese Massacre.

In fact, the level that was supposed to be the first I think is probably Field Ambulance, as it's the first in the list. After that it would be the Village of The Damned that would possibly be the intended second level and the possible next would be the Nuclear Plant (internally calls it Powerplant), the next would be Haunted Valley, next would be Ragnarok, next would be the Animal Farm (I hate that level, and btw, it's internally called Slaughterhouse.), next would be the Asteroids (First a farm now to Asteroids? as if that makes any sense..), next would be the Desert, next and the last of Chapter 1 (Internally calls it chapter 7) would be Loony Park.

In the next chapter, Riot, would be the first level, next would be Air Combat, the next would be the Cataclysm, next would be Dead Marsh, the next would be the Studios, and next would be Japanese Massacre.

After that, the Black Tower would be the penultimate level, and Sammael's Lair would be next, the final round. There would just be 2 chapters, not 3 the final has.

This a reason for all the different music orders, and the sudden jumps in difficulty varying from level to level in Overdose.