I don't think there IS a protocol. I'm from Eire yet I usually in fluent merican/anglo/Irish accent as thh vast m ajoriy of singers do. Probably because as someone explained to years ao, mot Country or Irush songs rely quite heavily on a strong R sound and in fct that R o ER                        sound forms the basis of most song. So when as is often the case onMudcat peopl criricuse singers for 'adopting' a fake American accent Yes just a few do. They are in fact simply adopting the international accent of song. As for Scottish trad, yes almost uniquely Scottich trad s usually sung om shok, horror, a SCOTTISH accent. But do not try copying i, it'l probabky just sound offensive unless you are a tkented mimic. Try trear it instead as an adaptation and do your own interpretation