In his book "Musicophilia: Tales of Music and the Brain," the late neurologist and best-selling author Dr. Oliver Sacks recalled the case of a patient he called D.L., who had a distressing lifelong problem. To her, musical melodies that gave other people pleasure sounded like unpleasant, random noise.
D.L's inability to hear music as others do first became apparent in childhood, when her father played various music recordings for her, and she was unable to tell them apart. She couldn't even recognize Gioachino Rossini's "William Tell Overture," which became famous as the Lone Ranger's theme song.
When D.L.'s hearing was tested, in some ways it appeared to be normal — she could hear human speech just fine, and had no difficulty distinguishing sounds such as the rustling of the wind, running water or a dog's barking from one another. She also could perceive rhythm well enough to become a skilled tap dancer. But peculiarly, when it came to pitch, she not only was unable to distinguish one musical note from another, but heard them all as a jarring cacophony — like "pots and pans being thrown around the kitchen," Sacks wrote in his book. Here's a video of him discussing D.L.
As it turns out, one Oxford study estimates that 4 percent of the population shares D.L's inability to hear music, but there isn't anything wrong with their ears. Instead, their problem is a disorder called congenital amusia, in which their brains seem to have an impaired ability to process differences in pitch.
Amusia was first described back in 1878. Canadian anthropologist and science writer Grant-Allen wrote about a 30-year-old man who could not recognize familiar melodies, carry a tune or "discriminate the pitch of two successive tones," according to a 2002 journal article published by University of Montreal neuroscientist Isabelle Peretz and her colleagues.
In 2002, the University of Montreal team published a small study in which they gave a variety of tests to 11 adults with congenital amusia. They found that the hereditary condition seemed to be related to severe deficiencies in processing variations of pitch — which, oddly, only occurred when the subjects were listening to music. Their ability to hear other sounds, such as speech, were unaffected. In one test, for example, they generally failed to recognize Christmas songs when they were sung but could recognize them when the lyrics were read aloud.
Stranger still, when the Canadian researchers did a 2009 study in which they monitored the electrical brain activity, they saw activity indicating that people with amusia could detect the same fine differences in pitch that the typical music-loving person can. The problem seems to be that they're not aware that they can hear music just as well as other people, because of glitches in how their brains process and remember the information.
A 2013 study by French scientists indicates that people with amusia may have structural abnormalities in their auditory cortexes and a deficiency of white matter — the insulating material that helps neurons to transmit signals rapidly — in part of their frontal cortexes. What that may mean is that information about sounds gets garbled and delayed slightly, just enough to prevent a person from identifying it as a particular pattern of notes.
It's not clear yet if there's a way to fix that problem, but as Sacks noted in his book, it's a comfort for people with amusia just to know that there's an explanation for their inability to enjoy the music that gives so much pleasure to others. In D.L's case, he wrote, her big regret was that her condition hadn't been diagnosed in childhood, rather than at age 70. "This might have saved her from a lifetime of being bored or excruciated by concerts, to which she went only out of politeness," he explained.