If you have never heard of the author, Oliver Sacks, I recommend that you take a read over the story of his life in the brief biography that can be found on Wikipedia; he has quite an interesting story.
This book by Oliver Sacks was the first place that I read of the idea that the use of music to show signs of recall in patients who seem to have dementia/Alzheimer's. The music ultimately acts as a trigger to memories, and with the activation of memories comes the recollection of names/vocabulary in general. Take a look at this video to see a great example of how music can assist those with dementia/Alzheimer's:
Note the incredible difference between this man's extent of vocabulary at the beginning, and the end of the video. The difference between the two is incredible. There is new research that may explain his behaviour, as the University of Utah has published some findings that suggest that the brains of people with Alzheimer's and dementia, while they may lose significant components of their memory, seem to hold on to many areas of their brain associated with music, and it seems relatively untouched by the dementia/Alzheimer's.