Pau_Diaz: After I installed the version of Mafia on offer on GOG. I noticed that a few more directories were added that weren't included with the original or Steam version. They were texture and sound folders. What did they contain and who added them to this release of Mafia?
If you use the offline installer of Mafia 1 without adding any mods, there are only 2 directories in the GOG version: "mafiaIItrailer" (wasted space on the hard drive, contains a trailer for mafia 2) and "sounds".
Since from both the Steam and GoG version licenced music was removed, my guess is, that the sounds folder does exactly that, it's there to override the default sound files. If that's how they did it, then all you have to do is to delete this directory in order to get the original music back. Otherwise there are several instructions here on the forum how to do it.