... there is no point to musical analysis at all unless it is 'two-dimensional' – unless [...] one examines the music in terms of what I call its 'Background' (and this 'Background' is the sum total of the expectations which the composer creates) and its 'Foreground' (and its 'Foreground' is what he does instead). That is to say, the composer creates certain expectations, well-defined expectations, which he proceeds to meaningfully contradict. There is therefore a strong relation between 'Background' and 'Foreground', between that which happens and that which lies at its back – or to put it the other way round, between that which the composer leads you to expect, and that which he does instead...

Hans Keller, Lecture on Beethoven's Op.130, BBC broadcast from Leeds University, 1973.