Thing One has taken piano lessons for four years now. He started at age 6, when I realized that he could pick out tunes readily by ear. His first piano teacher quickly determined that he has absolute pitch (also known as perfect pitch), meaning that he can identify any note correctly as soon as he hears it, without needing to first hear a reference note. He can also tell me what pitches he hears in elevator dings, train whistles, car horns, etc. It's pretty cool. I started music lessons as a small child as well, and I have pretty decent relative pitch, but nothing like his ability.
Thing Two started learning to play the piano this past summer. He wanted to try it: we had no idea how he'd do with it given the abstract nature of music theory and his language comprehension issues, but we didn't want to deprive him of the chance to try. A good call, as it turned out. He loves it, he practices like a fiend all on his own, and he's moving through the books at a rate that is startling the teacher.
Both boys are performing in a holiday piano recital at the beginning of December. Thing Two has two easier pieces and Thing One a single difficult piece. The other day, I walked into the living room and realized that Thing Two was playing a simplified (but still involving chords) version of Thing One's recital piece entirely by ear. There was no music in front of him, and he can't read Thing One-level music yet anyway.
Today, for kicks, I had him play that piece for the piano teacher. She looked at him strangely, then asked him to turn around on the piano bench so he couldn't see the keys she was pressing. Sure enough, he has absolute pitch too.
Speaking as a scientist. it's known that there is a genetic element to absolute pitch. Given that fact, you'd expect the siblings of people with absolute pitch to be more likely to have it themselves. Not so much of a shock from that standpoint.
In this case, we're talking about a kid with a severe auditory processing problem (in the words of his neurodevelopmental pediatrician.) A kid whose neurological circuits between his ears and brain are indisputably, deeply scrambled, with respect to both incoming and outgoing language. And a kid who is completely tone-deaf while singing, to boot. So to hear that his auditory perception with regard to incoming musical notes is perfect was a surprise, to say the least.
The brain: a wild and wonderful place. Wish we actually understood more than the tiniest fraction of how it works.