The original Doom had third-party audio playback routines, so the source came with a rewritten sound server: https://github.com/id-Software/DOOM/tree/master/sndserv

    The bad news:  this code only compiles and runs on linux.  We couldn't
    release the dos code because of a copyrighted sound library we used
    (wow, was that a mistake -- I write my own sound code now), and I
    honestly don't even know what happened to the port that microsoft did
    to windows.