In first link music plays wrong how it's not supposed to be, more like Fluidsynth or Modern style. This is when Wave Blaster is selected.
Second link is how the game playing midi in native, original, by default or Classic style. This is the way many fans remember music in that game back in the days, when music card was Sound Blaster (although even more retro hardcore dudes play midi in OPL).
But if you need that effect so much, you can change your music card from Sound Blaster to Wave Blaster in Setup.exe (in your Duke install should be Settings shortcut). ;-)
Post edited June 20, 2013 by HenitoKisou