There's a name for deliberately hosting a service that blatantly disregards copyright enforcement. It's called "contributory infringement", and the litigation of which will have existential amounts of potential damages.
It particularly shouldn't require YOU as web host to try to ascertain the legal status of every 100-year old sound clip. That's not realistic, as Youtube's experience clearly seems to show. It does require you to respond when someone sends a signed document claiming it's theirs.
I'm not a lawyer etc., would be happy to have this explained if I'm wrong.