Terry Teachout's newest post talks about Leonard Bernstein's television shows back in the late 50's through the early 70's that were called "Young People's Concerts". I only saw a few of them, but had the LP of the one he did on the first movement of Beethoven's Fifth Symphony, which I listened to over and over. He went through the sketch books and found earlier versions of what we now hear, orchestrated them and had the orchestra play them, one after the other, and then the final version.
Ever after that, I heard classical music differently, having had a window into the creative process - and never forgot his saying that what Beethoven finally came up with sounds "inevitable", especially after you've heard the ways he tried of doing things that didn't sound "inevitable". In my own occasional compositions I still use that way of listening - does every measure sound as though it were the inevitable outcome of the previous measure.