Beethoven composed his greatest works while almost completely deaf

By 1818, Ludwig van Beethoven was profoundly deaf — yet he composed the Ninth Symphony (1824) and his late string quartets (1825–1826) entirely in this period, work widely considered among the greatest music ever written. He reportedly felt vibrations through the floor and through a rod he held to the piano as he played. At the Ninth Symphony's premiere, Beethoven stood conducting facing the orchestra while a separate conductor kept time. When the performance ended, he did not hear the applause — a soloist had to turn him around so he could see the audience standing and clapping.

Source: Swafford, Beethoven: Anguish and Triumph (2014)