Cwm Rhondda - Guide Me O Thou Great Redeemer (Orig Jehovah)

Cwm Rhondda is my favourite Welsh Tune This is sung by a Welsh congregation in a Welsh chapel.
I am not Welsh but I love the traditional music that has come out of Wales.
I have uploaded this to try and make US listeners aware that the version they appear to play and sing is not true to the original tune and I want to know at what point it was changed :-) To me this change alters the character of the tune.