There's ethical considerations and there's legal considerations, and they aren't quite the same thing.

Nothing unethical about preserving and passing on music and songs that were performed in public. Legally it might be more complicated in some situations, theoretically at least, but hardly that likely.

I think michaelr hits the nail on the head: "It's easier to get forgiveness than permission." (In the improbable situation where someone finds a way of making money out of, it fair shares for the originators.)

Of course if Deckman;s "150 years ago" had been actually the case...