In his wonderful Musicophilia , Oliver Sacks describes a patient named Martin, who suffered meningitis at the age of three and was never mentally normal afterwards. He spent hours listening to operas and by the time Sacks met him in 1984, he claimed to have more than 2000 operates memorized, along with Messiah, the Christmas Oratorio, and all the Bach cantats. Sacks writes: “it was not just the melodies that he remembered. He had learned, by listening to performances, what every instrument played, what every voice sang. When I played him a piece by Debussy that he had never heard, he was able to repeat it, almost flawlessly, on the piano. He then transposed it into different keys and extemporized on it a little, in a Debussyan way. He could grasp the rules and the conventions of any music he heard, even if it was unfamiliar or not to his taste.”