Here you are, Jim. Knocked this up in about 10 minutes.

Folk Music: Often based on traditional folk music but since the 50s and the start of the second revival the term has gradually acquired a much wider meaning to include music written and composed by members of the revival. Today any music written in the style of traditional folk music or that uses acoustic instruments like the guitar and concertina is generally accepted as folk music.

This wider meaning came to the British Isles from America where it had increasingly been used since the 1920s. Skiffle and American folk music suddenly blossomed in the British Isles after WWII and this sparked an interest in British folk music as well as imitation of American contemporary folk music. It was pioneered over here by such artistes as Bert Lloyd, Ewan MacColl, Martin Carthy, The Spinners and The Watersons. Alongside the increasing interest in traditional folk music many artistes began writing their own material. Once Tin pan Alley saw the commercial potential it began to spread to a much wider audience and the genre was crossed with other genres such as rock music.

There you go. We won't all agree on that but it's as good as your dictionary definition of classical music.