you might get lucky on a 5.1 audio channel mix for removal...

But it's not like picking sultanas out of a cake that's baked.

The mix is all a whole and your not actually seperating anything whatever frequency you remove from the sound will remove everything on that frequency.

Even if you have a partial clash across frequencies with what you delete the voice may become hollow sounding or Boomey depending if you slice the top or the bottom end of respectivly

so you'll find sometimes you can do it and other times you will have a total clash or partial clash of frequeies and won't be able to remove the soundtrack score.