Wolf 3D Mac Version 1st Encounter midi files - some information
The music data in the game is stored in standard MIDI format, using custom patches (not General MIDI, so you can't play them on a General MIDI synthesizer unless you change the patches to something vaguely close to what they're supposed to sound like). If I recall correctly, the MIDI data is stored as resources within the application, and can easily be extracted with ResEdit (although to make a standard MIDI file with the results, the data has to go in the data fork, not into a resource). Anyway, here are the three MIDI files I extracted, with the patches changed to make them work with a General MIDI synth. Available here.