"Remember those that have fallen. May they never be forgotten."
Yeah, this is the Superintendents subtle way of guiding you to safety. A very nice touch, might I add. But, in order to get all 30 Audiophiles, you do have to do EVERY mission. The first 29 can be found without any of the missions being completed, if you've beaten it before. The last one requires Underground Access, which requires all missions to be completed.
I would gladly play through again, this installation of the series is easily my favorite.