<p>If you are going to define a variety of perfect pitch as the kind that cannot be learned or developed, then I would have to agree that that variety cannot be learned or developed. I would also agree that perfect pitch is extremely rare among speakers of non-tone-based languages, along the lines of 0.01% of the general population. However, more than half of the native Mandarin and Vietnamese speakers who have taken music lessons from age 5 exhibited perfect pitch in the study that I cited. I think that suggests that, while perfect pitch is indeed quite rare, a great many people are born with the ability to acquire it given proper early training. That ability decays rapidly if it is not exercised.</p>