My parents, who are both in the Côr Dyfed, seem to recall an informal choral society called "Cantorion Gaerfyrddin".

[Caerfyrddin = Carmarthen. Why the soft mutation, I don't know, but they do seem to speak a rather purist version of Welsh in Carmarthen. It may have something to do with "Cartref" = "Home", "Gartref" = "at home" or "in"].