1.) When he was about 28 he started having problems with hearing. By the time he was 44 or 45 he was completely deaf.
2.) He could not hear the music but he could feel the vibrations of the keys. They were all different and unique so he could tell the difference between each through the unique vibrations of each of them.
3.) It didn’t change as much. As long as he memorized the notes and vibrations he was fine. In fact, the music got better. He released 5 of his greatest pieces regardless if he was deaf or not.
4.) Yes he did! He composed great music during his deaf times.
