We're dealing with music that is being played by traditional instruments in a specifically built building called a concert hall.
But classical is not - the reference is wrong, because classical on one hand refers to one period in musical history, which is Mozart, Hayden, Beethoven, which is a fine period in musical history, but it was a while ago.On the other hand, it sort of alludes to some kind of "class," which A, is not true; B, is kind of detrimental to the whole idea. Because the point is that this music is available and it's actually relatively reasonably priced.