Bobby Prince: "This song was originally written for Wolfenstein which only supported FM synthesizers. In order to get into the mood for it, I rented a movie about the infamous "Doctor of Auschwitz" and watched it until I was totally infuriated. This song was the result of the feeling of evil that came over me thinking about the terrible things the Nazis did.
During the development of DOOM II, a decision was made (by John Romero, I think) to include at least one Wolfenstein level. This song had been one of John Carmack's favorites in Wolfenstein, so I translated the FM file to a general MIDI file. The FM version had an instrument that sounded like footsteps (for soldiers marching), and I had to try to find a similar sound among the 128 standard instruments that make up the general MIDI standard. It turned out that the gunshot patch (general MIDI instruments include several sound effects) would work if I played a very low octave note for a relatively short time. One would call this "using an instrument patch by abusing it." The problem with doing this is that not all sound cards have the same effect when you abuse individual instruments. Such is the case here. On some wavetable synths, these "footsteps" last long enough that you begin to hear the richochet part of the gunshot. On the Roland Sound Canvas and the Yamaha MU-80, it does sound like many soldiers marching. Such incompatibilities and quirks are the price one pays for trying to make something do what it was not really intended to do".
Map 31: Wolfenstein