Different versions of Memento Mori songs?

[Memfis]

Over the years I stumbled upon a few midis that sounded almost like the songs from MMMUS but a bit different. For example, Squadron 417's intermission song seems to be an edit of MM's one, or in odyssey.wad (the one with five maps based on historic locations) there is a different version of MM map05 music. Why are there different versions floating around, where do they come from?

[Alfonzo]

I'm not sure why map05's music would sound any different, but Klem's 1995 episode Cringe features old versions of tracks that were updated for release in MM.

[Doomkid]

There's also an example of this in Brit10.wad, where it basically sounds like a glitched-up version of MM2 music. I figured it might have been messed up when converted from MIDI to MUS, but who knows, maybe it was intentional. It sounds like crap compared the the non-fucked up version, though.

(It's this song, by the way: https://www.youtube.com/watch?v=2LKc3orJJhs )

[Memfis]

Fun to listen to these old versions, Cringe E2M7 (MM MAP02) sounds as good as the later edition and I like the more lively intermission. Perhaps the map05 one was posted on the internet or something...