The deafness bit has been overstated in terms of its ultimate importance on his work. Any great composer would have had no trouble composing while deaf. Mozart or Bach for examples and many lesser lights. For people with absolute pitch it's the inner ear that matters not the outer ear. The most significant thing about his deafness is that it deprived us of more piano concertos which at the time were only written for the composer to perform and which he obviously could no longer do.
Bach referred to composers who wrote at the keyboard as what translates best as Keyboard Cowboys and had nothing for contempt for them. He required all his students to prepare compositions complete at the desk before playing them.
And that was a man who could improvise a 5 part fugue at the keyboard if necessary.
So9