First, people on these forums have used My-Little-Pony-based avatars. That was really weird - I mean, you would probably have hard time to find two things that are more opposite than Doom and MLP. But MLP was like "internet cancer", so it was inevitable these forums became "infected" eventually.
But now you suggest to include classical music into Doom? I mean seriously, you want to replace fast and dynamic, metal-like Doom music with anything by Philip Glass? Perhaps more dynamic tracks like Mishima or maybe "Hymn" track from Akhnaten would be acceptable for Doom, but - of all possible choices - you pick Koyaanisqatsi? What does *that* have in common with Doom music?!? Erhhh, I'm probably getting too old for this.
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Hmm, on the other hand, most tracks in Doom 2 are crap (compared to Doom 1, anyway), so perhaps it would be not so... inapropriate. At any rate, you are welcomed to try. Here can be found several MIDI versions of Koyaanisqatsi:
http://www.jerry-nagasaki.net/midi_en.shtmlBut since Zdoom can play MP3 files directly, using MIDIs is somewhat outdated (well, except that little fact that all Koyaanisqatsi MP3 recordings are copyrighted and therefore should not be used in a Doom mod).