Watermark files per unique user and go after whoever leaks them.

Diff two copies and remove the diff.

I doubt they'd just add a UUID in a file header somewhere. If they uniquely modify the actual audio samples in a way that is inaudible during casual listening, that would be much harder to "diff", I think.

If it is inaudible then I can just remove the diff from both or overlap them or...

Can you guys catch up on the absolute basics of the last twenty years of audio watermarking research before continuing this conversation please dear god

Why not educate us oh wise one?

Are you saying that two audio files each watermarked for a specific different user will not show a difference? Because then I am genuinely interested in how they achieved that feat

That seems shaky in a lot of jurisdiction.

Watermarking might not be enough to prove that the person doing the distribution is the same one responsible of the leak. I fear at most it will be a contractual dispute between the person who received the watermarked file and the original distributor without the ability to easily link the overall counterfeiting charges.

But anyway, I don't think they really need to do that. They just need to shutdown any unauthorized distributors that make things too easy. As long as the friction introduced can convince people to pay a low subscription fee, they will be fine.