after doing a bit of googling the magic MIDSfmt, gave me this link https://www.vgmpf.com/Wiki/index.php?title=MDS for the "Midi stream" format It matches the time period and the header also matches. it can be played with foobar and winamp. Here is a player for it from the doomlegacy source https://sourceforge.net/p/doomlegacy/sv ... mid2strm.c