Perfect pitch, which is also called absolute pitch, is the ability to name any note (such as A, B flat, C sharp) just from hearing the tone, without reference to other notes in a scale.
Relative pitch, which is far more common, is the ability to tell what note is being played by judging the interval between its pitch and that of a reference note.
Each note in the scales used in most music is a sound resulting from a particular number of vibrations per second; for example, most modern pianos are tuned so that the A above middle C sounds at 440 vibrations a second.
How perfect pitch is developed or why some are born with it has been the subject of much study recently, and strong evidence points to both genetics and early musical training.
In a 1998 study of 600 musicians by researchers at the University of California at San Francisco, nearly all of those who had perfect pitch said they had started their training by age 6.
The younger the musicians were when they started lessons, the more likely they were to have perfect pitch. Those with perfect pitch were also far more likely to have family members with the same ability.
Brain activity in response to music is now being closely studied by techniques including PET scans, and researchers have found that the area of the brain involved in processing sounds, the auditory cortex, develops clusters of specialized brain cells that are more active in response to piano tones in skilled musicians than in others.
While that study found no difference in brain activity in those with perfect pitch, other studies have found a sound-processing region in the left brain, part of the planum temporale, that is relatively larger than the same area in the right brain in those with perfect pitch and is active when they try to name a note.
This difference was found, the researchers said, even though most music processing is done in the right-hand side of the brain.
One theory is that the overall contour and melodic functions of music may be handled by the brain’s right side, while the task of naming notes and identifying their pitch could be concentrated on the left.