If it’s mixed, you may be looking at a foley session to recreate the natural sound.
Else get your own music and substitute it for the audio on the DVD.
There is an alternative though — but you may find it extremely difficult:
Take the music (you would have to get a CD of just the music and not the natural sound) and add it then invert the waveform and hope that “cancels out” the music on the DVD.I have tried this once and was successful for a very short clip. Problem is, even with CD audio, the music may play back at different speeds. And the sound I got as a result was really “muddy.”
What if there were no hypothetical questions?