Sacks opens his discussion of the differences in peoples’ musical senses by comparing two opposite problems. In one case, a person has perfect pitch and tone, but dislikes music and doesn’t understand what makes music good or bad. In the second case, the person has a great drive to make music, but fails to sense tone or the other subtleties of music. For both people, their neurological abilities do not align with their desires. In a third case, a man with Tourette’s reported having such a strong inclination toward music from such a young age that everyone assumed it would be his path in life. Although he loved music, he felt it was something he had no choice about. Studies conducted in the 1990s by Gottfried Schlaug show several distinct structural features of musicians’ brains, such as an enlarged corpus callosum (the connecting area between the two hemispheres) and increased gray matter in the auditory, motor, and visuospatial areas of the brain. The longer and more intensely someone trains in music, the more pronounced these differences become. Sacks notes that, unlike language, music can be picked up and learned at any age, even when one is not exposed to it early; it seems that music is innate for almost all people, though to varying degrees.