Haha, I know what the MOD is, but its not a 3D file. Its an Amiga file for playing the old style track data used to make music.
Megadrive/Snes, etc, used forms of Trackers (module data) to create music.
Even Unreal Tournament on the PC for instance, uses MOD files, though in a different form, but still, the basic principles the same.
Its rather like MIDI, but uses wave sample data instead of a MIDI bank to play the tracks.
You can get extensions for Winamp to play almost all forms. I have about 5,000 at least MOD style music files on my computer.
Different forms range from:
GYM - Megadrive MOD,
SPC - SNES
and then theres tracker programs data formats like:
XM,
IT,
MOD,
etc.
All basically the same in how they play though.