"Examination of Mozart’s surviving sketches and drafts—Constanze threw many sketches away—reveals that the composer sometimes began a piece, set it aside, and resumed it months or years later; rewrote troubling sections several times in a row; started movements from scratch when a first attempt failed to satisfy; and waited to finish an aria until a singer had tried out the opening. Ulrich Konrad calls these stockpiles of material “departure points”—“a delineation of intellectual places to which Mozart could return as necessary.” In other words, the music in Mozart’s mind may have been like a huge map of half-explored territories; in a way, he was writing all his works all the time. The new image of him as a kind of improvising perfectionist is even more formidable than the previous one of God’s stenographer. Ambitious parents who are currently playing the “Baby Mozart” video for their toddlers may be disappointed to learn that Mozart became Mozart by working furiously hard, and, if Constanze was right, by working himself to death."
I was really happy to come across this article called A Storm of Style by Alex Ross in the New Yorker. The article speaks for itself: no comment is needed. I'm glad that a "hard copy" will be arriving in the mail shortly because this is one I would like to read many times.