“Does every performance of a Mozart sonata only include what Mozart put there? I remember years ago a very interesting conversation where somebody asked Milton Babbitt that question. Babbitt had noticed something very provocative in one of the symphonies of Mozart, something about the way Mozart used a certain register only for certain instruments, and it really was the kind of thing you’d expect Babbitt to do, and a kid put up their hand and said, “Mr. Babbitt, did Mozart put that there?” and Babbitt said, I think quite aptly, “It doesn’t make any difference.” ”

– Bruce Brubaker interviewed at New York Pianist, via his AJ blog, PianoMorphosis