@iska The music for Deus Ex and Unreal Tournament was written in Impulse Tracker format, but shipped in the Unreal engine-specific container format UMX. Wikipedia also claims that the first Unreal was like that, but I dunno the actual history. Guess you could find the composers on twitter and ask.
The original notes for the unreal engine only mention IT.
@grey@iska lots of tracker artists for both games, everyone being used to this or that MOD filetype + programmes van den bos made mostly in Impulse Tracker brandon, sega, and some others, made in Scream Tracker (s3m)
@iska Seems simple enough to go find the original Unreal umx files and see what they contain. Unfortunately archive.org is being attacked right now so the iso links are all broken. RIP.
@iska Just to followup on this, checking with the original sources shows that we were both right, Unreal was S3M in a UMX container, UT99 was IT in a UMX container.