Abnormally hightened sense of pitch perception, allowing one to do most (if not all) of the following:
* Correctly identify a musical note by name without any reference tone.
* Correctly sing a musical note at whim without any reference tone.
* Correctly identify the key a song is played in without any reference tone.
* Discern how sharp or flat a musical tone is, relatively speaking, without any reference tone.
Also (more accurately) called absolute pitch
This ability, possessed by about 0.01% of the population, can be very helpful.......or almost useless.
No, you don't necessarily have to be born with it.
Traci astounded the rest of her band by effortlessly naming random notes they played. She has perfect pitch.