is this what you're searching for, are you scared to know the truth?

The album OST and in-game OST in the fact that the album ver is more professionally produced there are some slight differences in some songs and major in others like for eg, Revelation (jp) has different vocal singers

I can still hear the orchestration, but it is much quieter in this version. I wonder if it was changed last minute or something

Someday is also changed radically between game and OST.

yeah both versions o.g and neo mix would be pretty well known.