Early Music covers everything that requires historic research - medieval, renaissance, baroque, classical are all covered! I doubt the term covers Sting and The Amazing Blondel, though they've obviously been affected by it, as many Pop artists have down the years - Gentle Giant, Gryphon, Third Ear Band, etc. - all gave just stirring medieval tinged pop music, but, although very much a product of its time & ultimately a key to a particular zeitgeist (i.e. the early 1970s) is it not Early Music per se.