Favourite music quote: "From the heart, may it return again to the heart!" (Beethoven)
Sums up music perfectly.
Can anyone explain how a deaf composer composes such hopeful and wonderful music, such as the 9th Symphony (Ode to Joy)?
Well he wasn't deaf for his
entire life. I know he was deaf by then but I think it helps that he had a very musical life regardless. I feel as though provided you've had such an exposure, even if you start going deaf you can still "hear" it all in your head anyway, or at least how you imagine it would be heard.
That and there's probably also some melody/harmony writing techniques that you could employ anyway. Although Beethoven was going into the Romantic era he still had some classical techniques. (By the end of the classical era a lot of composition techniques were becoming common, even though they were about to be dominated by others.)
Although having said that, in my opinion, the most profound change from his deafness was the style of music. When I compare Pathetique to Appassionata for example, I just feel that the first is somewhat "more rigid" than the second. And I feel music that delves too far into the Baroque/Classical periods just feels comparatively more blunt.