I am always uncomfortable with the use of 'classical music' as a catch all expression for that which exists outside the genre of popular music.
How does one define "popular music"? Offenbach, Lehard, Strauss II etc... were all the "popular music" of their time. To a great extent, the same can be said of Mozart, Dowland, or many examples of medieval or Renaissance folk music ("Greensleeves"?).

