I wasn't hugely impressed with this. Sacks's writing sometimes gets extremely dry as he goes into the technicalities of how the brain functions. I found his other books, with chapters each covering a variety of conditions ("Anthropologist on Mars," "The Man Who Mistook His Wife for a Hat"), to be much stronger, even though they were less consistent thematically. It seemed that at times Sacks had to stretch to find patients with some of the musical conditions he described -- not a good sign, since some of his best work consists of describing individuals' conditions and then working out what might be causing them. He also borrowed heavily from cases described in his other works. It made me wonder, what would motivate someone to write a book if he didn't have the necessary new material?

...infants at six months can readily detect all rhythmic variations, but by twelve months their range has narrowed, albeit sharpened. They can now more easily detect the types of rhythms to which they have previously been exposed; they learn and internalize a set of rhythms for their culture. Adults find it harder still to perceive "foreign" rhythmic distinctions.