Interestingly, the music is different based on the audio you select. If you listen to the PC speaker version of the theme, you might notice that the final note is arpeggiated, which isn't true for the midi version. The PC speaker version is also missing a note in the previous measure that exists in the midi.
Then when the opening credits have finished and the game begins, there is background music for the lookout if you have midi audio, but silence for the PC speaker.
I wouldn't mind figuring out how to get a midi to sound like the PC speaker. Setting a square wave synthesizer as the instrument doesn't do it.