Beethoven heard music through his teeth

Beethoven began losing his hearing around the age of 27, and towards the end he could barely hear at all. Yet he composed some of his most monumental works while deaf. How? Partly through a physical trick: according to several accounts from his time, he would rest a rod against the piano and clench it between his teeth. The vibrations travelled through his jawbone to the inner ear, bypassing the damaged parts. That principle — bone conduction — is the same one used today by many hearing aids and sports headphones.

The most famous moment came in 1824, at the Vienna premiere of the Ninth Symphony. Beethoven, standing with his back to the audience, kept beating time after the orchestra had finished. The contralto Caroline Unger had to turn him around gently so he could see what he couldn't hear: the whole theatre on its feet, applauding.

He saw his triumph instead of hearing it.