For anyone with an interest in neurology and music, there is another article by Oliver Sacks in the current New Yorker. Free!
The unfortunate subject of the article was stricken with a viral encephalitis, and lost important parts of his brain, mainly affecting his memory. He remembers nothing that happened less than 20 years before his illness, and is incapable of forming new memories: he has no recollection of what happened just seconds earlier.
The things he does remember: his wife and children (the only people he can recognize); and music.