The difference between American Idols and the karaoke-challenged may be more than voice deep. Researchers have found that tone-deaf people have an unusual distribution of neurons in the front of their brains.

Tone-deaf individuals cannot recognize familiar songs without lyrics and do not realize when their own singing is out of tune. About 4 percent of people carry this trait. Previously researchers have hunted for the roots of this musical inability in the auditory centers of the brain. But they did not find any differences in these regions between tone-deaf and normal listeners. So Krista Hyde of the Montreal Neurological Institute at McGill University and her colleagues scanned entire brains to search for anatomical anomalies. They found that the amusical subjects had less white matter—neuron axons that are wrapped in an insulating sheath of myelin—in the right inferior frontal gyrus. The worse they performed on musical pitch tests, the less white matter they had.

Such individuals also had more gray matter—unmyelinated neurons—in the same region. Other imaging studies have recently suggested this brain area plays a role in musical-pitch processing and memory. This neuroanatomical difference could be the result of neurons not migrating properly during development. Similar malformations are associated with neural developmental disorders, such as dyslexia. “Tone deafness might be analogous to something in language,” Hyde says. “These disorders exist in language, so why not in music? One can argue that music is another language.” Uncovering these brain differences could lead to treatment for tone deafness, he adds. That could be music to many ears.