I don't know the words but I remember watching his funeral on TV. They sang special words to Land of my fathers that were written for the occasion. It's a long time ago but I remember the chorus, instead of "Wales, Wales" began with "Nye, Nye". I doubt if that's much help but it might be traceable. Good luck. When I grew up, my father thought he was a saint and my mother thought he was working for the devil so their disagreements impressed him in my memory.