After a short search, I found this.

DX music is in .mod format, which works like a modified MIDI file -like a MIDI file with the appropriate soundbank attached-. This proprietary soundbanks (for lack of a better term) are put together by the composer, sometimes even on a song by song basis. And the sounds that comprise them are not necessarily setup to reflect the actual pitch the sample is sounding. So if you open a DX music file on a tracker program and you sit down with a piece of manuscript paper you might be able to actually transcribe the track, but an automatic conversion would be subject to error in the given example.

Also, sometimes there are effects written as notes into the tracks (ie: the beginning of “Synapse” or the “UNATCO HQ” tracks where the melody is written with a delay in mind to form a counter-melody with the original phrase. If you look at the track in the tracker program a simple algorithm wouldn´t be able to identify this. You´d have to implement phrase recognition features and my guess is that is much more troublesome and un-educational than a DIY approach.

So, pretty much not going to happen. But it was a nice thought.