Imagine being a musician who slowly loses his hearing. That is exactly what happened to Ludwig van Beethoven. He began having trouble hearing when he was still a young man, and over the years it became worse and worse. For a musician, this was a terrible thing to happen. But Beethoven didn't give up. Even when he could hardly hear anything at all, he could still imagine music inside his head. He used those ideas to write some of his most famous pieces. Imagine sitting at a piano and not being able to hear the notes! Beethoven even wrote his amazing Ninth Symphony when he was almost completely deaf. When the music finished, the audience clapped and cheered — but Beethoven couldn't hear them.