As a percussionist, and having played timpani for five years now, I can vouch for the usefulness of perfect pitch. Although I don’t think I have it, it comes in handy when trying to tune them. Tuning kettledrums (without the use of a pitch indicator on the side of the drum) involves pushing a pedal up or down in order to reach just the right note, sometimes within a VERY short amount of time. If a timpanist does not have perfect pitch, then there is a definite need to get relative pitch in a hurry, often by having a mallet player give him/her notes. There is nothing more embarassing, to me, than having a band director waiting on you to get pitches from the bell player while the audience patiently waits - thus the usefulness of perfect pitch.