Beethoven used a metal rod to feel the music.
Why it is true
After becoming completely deaf at age 40, Ludwig van Beethoven held a metal rod between his teeth and pressed it against the piano to feel the vibrations of the notes. In this way, he continued to compose some of his most important works.
Source: Music History
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.