itch.io

Alas we don't have discord. Well, it's a moot point at the moment because their net situation has gone south - but it would be put together either as bgm for a text-only story, or bgm for a podfic (recording) of the story. If you're concerned about it being collected elsewhere, the first would have to go on Web Archive as its own file, but if you're not cool with that then with the latter, the podfic file would go on Web Archive, and then that file would be posted to AO3. They're both embedded _in_ another project, but technically the difference is whether the file is separate. It's basically the same as putting music in the bg of a visual novel online. Just very low-tech.

Web Archive is basically just the host for the single file; but it is a searchable archive of, well, the internet, so it's not inconceivable that someone would find it that way by searching your name or the title. (In fact I see by my browser plug-in that your homepage here on itch is already archived by them, by at least 2 users. Edit: I should also add, if you have those music files floating around anywhere public, chances are good Web Archive already has them somewhere. Likely unlabeled and unattributed, unless they backtrack into archives of your site(s).) It doesn't matter if I figure out how to host it for them; AO3 has a finite number of sites that they'll allow embedding from, and ours are disallowed.
In other words their Web Archive "home page" is not put out, well, anywhere, and is unknown unless you've already visited their AO3 page. They're not stockpiling music. I don't think there are even any other playlists involved. On Web Archive I believe the label is 'Community Audio' which is separate from the music section.

Anyway I hope that clears up the technicalities of it. Thanks for the prompt response!