I came across most of the original source MIDI files for the original Doom and Doom II when going through the various official ports that have been made to various systems. Unlike other ports that utilize MIDI music, the OS/2 port actually uses the original source MIDI files as its music and not some MUS2MIDI conversions. Even better, it does not include just the shareware MIDI files but also the registered and most Doom II midi files (ULTIMA and READ_M are missing for some reason). The following facts about these MIDI files support them being the original material: