To a casual observer snooping the relevant network, it would probably (as here) look as elevator music, but to the intended recipient who can decode the steganography, it would be a covert listening device.
Or you could have an extremely long audio file so the repeat situation doesn’t occur.
The decompressed data is always the same, but the data in the dictionary used is where you store your sneaky bits.
Sure, that's still mildly suspicious. But way less than the actual music data changing all the time.
You can use a channel with lots of noise, because you can use error correcting codes to to restore the intended message.
(To elaborate with an example: sometimes a package might already drop randomly, or timings might be slightly delayed anyway.)
I guess you could also build an auto-auto-tune or auto-remix solution so the songs always have justifiable variation without needing fully generated music.
-edited because it didn't make sense before
Not just decode, but also decrypt.
You'd probably want to encrypt not just for the secrecy, but so that the noise introduced by the steganography doesn't seem so suspicious.
If the music was repeating but the stream was different all the time, then steganography could be the reason :)
In fact I don't think I've every been on an elevator that had music.
Google sez: Music for Airports was installed at the Marine Air Terminal of New York's LaGuardia Airport for a brief period during the 1980s.
Elevator music may no longer be a thing, but apparently, airport music still is:
Basically, you'd use steganography to hide that you send a message. And that message would be encrypted. You can use almost any standard encryption scheme, as long as you remove headers etc. Any ciphertext of a crypto-system worth its salt will be indistinguishable from random noise without the key.
Weirdly, my Sonos/Unifi issues are gone at the moment, but wow is it painful when you hit it.