It's just like trying to crack a password, only that it's one-time padded. How would you know that a certain 5 minute chunk of sound was minutes 2 through 7 of the 18-1/2 minutes of the Nixon tape that got erased, or some other conversation that Nixon had when he was talking to Abraham Lincoln, and could that have had the sound of a steam train or a Toyota Prius's generator overlaid in the background. The sound would exist in the set of all possible 5 minute songs, but you'd never know when you unlocked the right one. The United States does not forbid the listening to VLF radio transmissions intended for submarines for this same reason. It's probably really classified military information, even if you found a meaningful sequence of characters, you would have only discovered one of many sets of messages, some of which aren't even secret. Likewise it's theoretically possible to generate all possible 5 minute songs, though it's quite computationally infeasable.

And there can be different songs on 2 identical vinyl records pressed from the same master mold, one was just played one more time beforehand. Or it could be a microphone recording it from a cell phone speaker and another one through a $10,000 audiophool system.