I just loved Edmund Morris’s description of the creative process revealed by Beethoven’s manuscripts:
Beethoven’s manuscripts are revelatory, because he was an intensely physical person who fought his music onto the page, splattering ink, breaking nibs, even ripping the paper in the process. Not for him the serene penmanship of J. S. Bach, whose undulant figurations sway like ship masts over calm seas, or the hasty perfection of Mozart, or the quasi-mathematical constructs of Webern. Their writing is the product of minds already made up.