An observation rather than a criticism; and likely in part my fault for not being more specific in my earlier remarks. Nevertheless, it is my experience that artists, in particular, need to pay close attention to detail.

Your other, related thread (Mentra Gwen, neu Cwynfau y Wraig Weddw) suggests that you are making a serious study of the song/melody and its various ramifications, so it will do you no harm to ensure that your conclusions are as accurate as possible. If you have not so far done so, you should certainly consult the Bronson article. You will find it helpful.