"Perfect pitch or, more correctly, absolute pitch is defined as an ability to effortlessly name a note or a group of notes without comparing it with any external reference tone (my italics) when they are sounded, also people with perfect pitch can produce the note in instrument or via voice when it is told."

The jury appears to be out as to whether it is an innate or learned ability but current research seems to suggest it is a combination of both. i.e. there is both a genetic and a learned component.

Those who possess absolute pitch say it is a mixed blessing. I can remember clearly reading a letter in one of the UK broadsheet newspapers many years ago (Telegraph, I think) from a man with absolute pitch who had been to a concert of music by Bach played on "authentic instruments". He had been looking forward to the concert and had been disappointed because the orchestra was "out of tune" and had played a semitone flat throughout the whole concert. This had spoilt it for him. He was unaware that the orchestra had been tuned to A=415, that pitch standard being relatively new at the time. I think the letters editor or the music correspondent of the paper had added a note to the letter pointing this out.