Sufyan: The question is not that simple. There is only one "official soundtrack" or soundtrack album. The actual in-game tracks are loops and are not very functional as listenable soundtracks without editing. The GOG downloadable soundtrack is probably ripped from the separate Audio-CD that was bundled with the boxed "Game of the year" edition where these loops were edited and mixed to have a beginning and end.

The in-game music has always been one and the same. Perhaps you are confusing the details around the mistake made for the last official patch for the game where one of the Hell's Kitchen maps was reverted to a build that did not play music as intended?