A recent comment got me to thinking about the difference between perfect pitch and relative pitch.
I've had a conception of perfect pitch for a very long time. I know two people who have it. One of them is a former relative, and for this reason, and a continually mounting list of anecdotal evidence, I believe that one of my kids either has perfect pitch or a very highly developed sense of relative pitch. And I know a multitude of people who have relative pitch. I even had very accurate relative pitch for about 6 years.
Let's look at the difference real quick. Many say (and studies attempt to prove, as early as 1916), that perfect pitch is a genetic trait. It involves some or all of the following abilities:
* Identify and name individual pitches (e.g. A, B, C#) played on various instruments
* Name the key of a given piece of tonal music
* Identify and name all the tones of a given chord or other tonal mass
* Sing a given pitch without an external reference
* Name the pitches of common everyday occurrences such as car horns
Generally, it's the ability to identify, play, or sing a named pitch without the benefit of a reference tone or pitch.
Relative pitch is more common among musicians, and, by contrast, connotes the ability to identify:
* the distance of a musical note from a set point of reference, e.g. "a perfect fifth above middle C"
* the intervals between given tones, regardless of their relation to concert pitch (A = 440 Hz)
It is the skill used by singers to correctly sing a melody, following musical notation, by pitching each note in the melody according to its distance from the previous note. Alternatively, it is the same skill which allows someone to hear a melody for the first time and name the notes relative to some known starting pitch.
Using these differentiators then, we infer that perfect pitch is an already-residing internal ability, or at least that there is an already-residing reference pitch, readily accessible by the brain, and relative pitch is a learned and trained trait or talent.
It is said that perfect pitch is not a learned trait, and that relative pitch is in fact a learned trait. I believe there is some sort of ego in play there, in that those who have perfect pitch say that if you learn perfect pitch (to which one can indeed come very close), you have effectively learned relative pitch to a near perfected level. Those with perfect pitch like to think of themselves as some sort of lucky (or unlucky, as the case may be - more on that in a minute) genetic specimen. And I tend to agree to some degree. I once payed a game of trivial pursuit with a person who has perfect pitch, and who ALSO has a very very highly tuned sense of relative pitch (the two aren't mutually exclusive). One of the questions that came up in the game was something to the effect of, "What musical key does a 1970's model Cadillac horn honk in?" She thought (silently) for about 3 seconds, and said, "F Major 7". And she was right. She didn't need to have a reference tone, other than that one which she had constantly available for her immediate use.
Some owners of perfect pitch report that they have different tones in their heads - perfect pitch doesn't mean that you have a constant A440 ringing in your head. It can be any pitch, but it is consistently the same pitch for each individual.
So that's my reference point and exposure to perfect pitch. Here's my experience with relative pitch. During the years of junior high, high school, and a couple of years beyond that, I was literally immersed in music. Besides the casual listening, which I still do heavily to this day, I was almost always in two or three different school bands and two or three school vocal ensembles. I was also taking private lessons for both instrumental and voice, along with performing in an all-city choir, learning the guitar, singing in the city opera chorus, was the conductor at least one other chorus, recording music as an engineer/producer, and I was constantly auditioning for a litany of musical theater stuff, going to concerts, doing sound reinforcement for other productions and concerts, and supporting friends who were doing the same as me. At one point, I was able to sing, with very close proximity, about any pitch one would name. Later, when I was in college, part of the program I was in was an ear training class, where the teacher subscribed to the theory that tones, or pitches, each had their own color, and if you listened to them enough in controlled environments, you could identify the pitch by its color. I still do that to some extent today, although the skill has greatly diminished in me now, but I did do very well in that class.
So those are my personal relationships with both Perfect and Relative pitch. It was with this experience that I looked up both items on Wikipedia today, and learned a few other things. It seems that there is some evidence through studies in the 1990's and early in this decade that call into question the idea that perfect pitch is strictly a genetic, or inherited, trait. There is a study referenced there that shows a more-than-regular occurrence of perfect pitch in countries where the language is based on a tonal pattern as well as a series of simple vowel sounds interrupted by glottal stops, as most western languages are. Those languages are found in the eastern Asia area, as well as some parts of Africa. With more "official" perfect pitch instances in those areas, we can draw the inference that perfect pitch may be influenced by Nurture, rather than strictly Nature, as has been asserted. There is also a study that shows a window of time in very early development where the brain is susceptible to learning perfect pitch, but also shows that window as very definitely closed by age five. This shows why the Suzuki Method is so successful and produces some amazing string players.
If you're interested, you should check out the two Wiki pages for perfect pitch and relative pitch.