Have you ever wondered how a musician can pick out a single wrong note in a complex piece of music? Has anyone told you that you are tone-deaf or have a tin ear? These all relate to a sense of pitch—roughly speaking, the highness or lowness of a sound. It's what distinguishes a soprano from a bass singer and gives each piano key a distinct identity.

Our ability to distinguish pitch is not fully understood, but we do know that it involves some processing by the brain after a sound is perceived. This means tone deafness is not necessarily linked to any hearing disorder. An individual with perfect hearing may still have trouble distinguishing pitch because of how the brain interprets the sounds.

Research shows that 2 to 5 percent of the U.S. population has problems with pitch perception. Studies in twins also indicates that the role of inheritance in deficits in pitch recognition is extremely high, with little effect of environmental experience. Tone deafness appears to stem from nature, not nurture.

Want to test your own sense of pitch? We've developed an online version of the Distorted Tunes Test, a standardized survey in use for over 50 years. In it, you'll listen to a series of snippets from well-known tunes—some of which have been distorted by changing various notes' pitch. Your task is to pick out the incorrectly played tunes.