Thank you kytrad."England, ireland, Scotland, Wales mostly, with remnants of folk from several other countries " says it all. "Celtic" is a very useful term for classifying language families(but do remember the people concerned didnt call themselves Celtic. An academic linguist started using the term to classify their languages, and the term then started spreading). The most cursory glance at the surnames of oldtime musicians shows that the Celtic/Gaelic/Irish-Scots stuff you read about Appalchian or oldtime music can only represent a fraction of the truth.Folk music is wonderful, and true to life. Its origins dont need fictionalising, the reality is so much more lovely.