Very balanced, clear and precise explanation of the "commercial" use of the term "Celtic" as an umbrella for a diverse range of musicians, usually used without an authentic meaning

There's irish folk ,Welsh folk,Scottish folk,cornish folk,Manx folk,for uk I suppose you could say these regions are to a greater or lesser extent still celtic to some extent,in heritage,however celtic is a very general term,perhaps harps were in existence during the late celtic periods i believe there are illustrations of harps ,on old irish manuscripts,drawings,and also pictish carvings showing harp players to the celtic period ie pre 10th century ad.,no doubt drums,and basic flutes whistle flutes,the Welsh pibgorm,was possibly in existance in the late celtic period ,ie before the tenth century ad,ie before the english invasions of ireland Wales Cornwall and Scotland,what unites celtic regions in uk is language, early music in these countrys can be found in written form,perhaps to medieval times,just research,I think irish University sources could be useful ,if you go to France breton folk music might have a similar sound to eg irish,but how far back that similarity goes?also galicia in Spain might be another sound comparison?you need to research how far back the tunes have a similar sound if at all.

It's all semantics, pretty much: folk music is folk music. There are regional variations, of course... The idea of "Celtic music" stems mostly from 19th century nationalist movements: before, there was "Breton music", "Irish music", "Scottish music", etc.; but the idea of a "pan-Celtic" identity created the notion of an overarching genre called "Celtic music". Let us appreciate all types of music for what they are, and not try to force them into artificial divisions.