From The Art and Popular Culture Encyclopedia
Celtic music is a term utilised by artists, record companies, music stores and music magazines to describe a broad grouping of musical genres that evolved out of the folk musical traditions of the Celtic peoples of Northern Europe. As such there is no real body of music which can be accurately be described as Celtic, but the term has stuck and may refer to both orally-transmitted traditional music and recorded popular music. The latter sometimes has barely even a superficial resemblance to folk music of any of the Celtic cultures, but on the other hand it sometimes represents sincere work towards adapting Celtic traditions for modern, global culture.
Celtic music means two things mainly. Firstly, it is the music of the peoples calling themselves Celts (a non-musical, primarily political definition), as opposed to, say, "French music" or "English music." Secondly, it refers to whatever qualities may be unique to the musics of the Celtic Nations (a musical definition). Some insist that different ostensibly Celtic musics actually have nothing in common – such as Geoff Wallis and Sue Wilson in their book The Rough Guide to Irish Music – whereas others (such as Alan Stivell), say there is.
Often, the term Celtic music is applied to the music of Ireland and Scotland, because both places have produced well-known distinctive styles which actually have genuine commonality and clear mutual influences; however, it is notable that Irish and Scottish traditional musicians themselves avoid the term "Celtic music," except when forced by the necessities of the market. These styles are known because of the importance of Irish and Scottish people in the English speaking world, especially in the United States, where it had a profound impact on American music, particularly bluegrass and country music. The music of Wales, Cornwall, the Isle of Man, Brittany, Galicia, Cantabria and Asturias and Northern Portugal are also considered Celtic music, the tradition being particularly strong in Brittany, where Celtic festivals large and small take place throughout the year, and in Wales, where the ancient eisteddfod tradition still occurs. Additionally, the musics of ethnically Celtic peoples abroad are vibrant, especially in Canada and the United States.