Well, typically how it works is that it’s an alternative to renting a piece of farmland in cash. Instead of paying the land owner in cash, you pay them in a portion of your harvest. /s

You need to read Asimov’s The Last Answer.

What if instead you hid an encrypted signal within an otherwise perfectly legible audio signal? Imagine a song being played. To the ear the song seems perfectly normal. But, unbeknownst to a casual listener, there is an encrypted signal embedded within the audio signal. For example, data could be embedded within a song by ever-so-slightly raising or lowering the pitch of a song multiple times per second. Then if you had a copy of the original file, software could compare the original file to the song transmitted over the radio. The locations where the pitch rose or fell could be noted, and the data could be retrieved. You could send encrypted data without anyone realizing you’re sending encrypted data. To anyone else listening, it would simply sound like a song or other audio track being played.