Talk about a long voluntary - but 15 hours?

I thought that, when I read about the 600+ year organ piece (Organ2/ASLSP) to be performed on an organ in Germany, that was just people going mad. After all, it did allow several years (every time there was a rest in the music) for the church to get on with normal life (or is that not allowed? Must check that - or can I be bovvered?) , but apparently someone else it taking it seriously. Well, that's better, at least we'll hear the piece in its entirety in one lifetime.

But John Cage is dead. If it stops, will anyone hear - like in a forest, if a tree falls... (or a man speaks?)