At my saxophone lesson this weekend, my teacher asked me to sing what I was meant to be playing. It was pretty excrutiating and it took me a few attempts to hit the notes correctly. Fortunately, I’m not completely tone deaf, just a little out of practice. It’s estimated that tone deafness (congenital amusia) affects 4% of the population . It can be inherited from your parents which indicates that your genes are involved.
The problem is hitting the right pitch (or frequency) when singing. But is the cause hearing impairment, or does the difficulty lie with cognition or vocal production? Although the term tone-deafness implies a hearing problem, recent studies indicate that the name is probably misleading. It appears that the cause of the poor singing is within the brain, in particular the connections which link the perception of music and the production of the sung notes  .
 Peretz, I., Cummings, S., and Dube, M. P. (2007). “The genetics of congenital amusia (tone deafness): A family-aggregation study,” American Journal of Human Genetics 81, 582-588.
 Peretz, I., Brattico, E., Jarvenpaa, M., and Tervaniemi, M. (2009). “The amusic brain: in tune, out of key, and unaware,” Brain 132, 1277-1286.
 Loui, P., Alsop, D., and Schlaug, G. (2009). “Tone Deafness: A New Disconnection Syndrome?,” Journal of Neuroscience 29, 10215-10220.