I've been fascinated by perfect pitch. I studied theatre before a bizarre turn of events eventually settling into software engineering, so I got to meet a lot of extremely musically talented individuals, and out of those I've met only one with perfect pitch.

I peppered them with questions- I asked how long they've had it and they explained that they learned music (piano) at a very young age. They can recognize a single note, even chords. They can also be given a note to sing. I asked if they needed to hear other notes in order to distinguish it and they said no, they can hear a single note and know exactly what it is. I have always been fascinated by this.

Not related to perfect pitch, but I've trained myself to somewhat replicate this through relative pitch. I quitely hum to myself the lowest note I can (which just happens to be a C natural), and from there I can mentally step up and down the scale chromatically to find whatever note I need. I'm accurate to about a half step but no more than that, sad to say.