"Do you have perfect pitch?"
People liken having perfect pitch to possessing some kind of superpower one might come across watching too many episodes of "X-men" or "Heroes." That ability to sing any note upon request, or guess with 100% accuracy the name of the note in front of them is indeed a rare ability that many people would pay to have. (In my experience, I'd say a little more than half of the people that claim they have perfect pitch actually do. LOL)
Most people that have perfect pitch are conscious of their ability at a young age. A large percentage of them become musicians, eager to use their new powers. They ace their way through ear training and musicianship classes fine tuning their ability. Meanwhile, their fellow classmates are left in the dust struggling to learn the relationships between pitches and how they exist relative to each other. For those that come with a pre-installed piano in their brain, sight-singing exams are a breeze—singing a tritone interval is much harder if you can't summon this piano at will.
The advantages of perfect pitch don't stop there. As these perfect pitchers master their instruments, their (now fail-safe) skill becomes a sixth sense, like a buzzer going off every time they play a wrong note. In no time at all, they are executing flawlessly.
However, what matters in good playing is not just playing the right notes, but playing in context. One must be dynamic and be able to make small tuning adjustments so as many chords as possible ring perfectly throughout the concert hall. In other words, "A" won't always be at 440hz, it will be slightly higher or lower depending on its function, or what everyone else is doing. This contextual playing is important in all groups, but paramount in unaccompanied singing.
Why? Mainly because singers aren't perfect. Even the best vocal groups will unintentionally modulate up or down a little in rehearsal or performance. This is never a good thing, but it happens, all the time. However, it is still possible to have a successful "in-tune" performance as long as the parts are internally in tune. Modulating down a half step over a 3-minute piece is not as noticeable if the parts are internally in tune. There is nothing worse than having pitch heroes (perfect or not!) trying to keep the pitch up/down against the ensemble's will - they can make it sound much worse.
Ensemble singing requires a strong relative understanding of pitch, a skill that is often underdeveloped in perfect pitchers who I believe have relied too heavily on their sense of fixed pitch. Their sense of fixed pitch is so strong, that simply transposing the score up a half step can be a difficult task, but not for those musicians without perfect pitch who have developed a purely relational understanding of pitch. They may have been left in the dust in theory class, but they can transpose with ease and make the necessary adjustments to tune in context. This flexibility allows the singer to adjust to the ensemble in a way that brings to light the beauty of what the human voice can do. Unlike instruments, where a note is played using a specific fingering or position, the singer has the flexibility to place each note in its rightful place allowing for the most perfect tuning of chords, sonorous and out of this world. This is what I love about choral singing. The dynamic nature of pitch in ensemble singing is best suited for those who have a solid relational understand of pitch.
Some of the best singers in the area have perfect pitch, so I don't want to discount them and their wonderful singing. However, I do see this as a general problem and want to take perfect pitch off the very high pedestal the music world has put it on.