Granted, it's a prank you can play on only 1 in 10,000 people. But if you find one of those rare individuals who can name any note they hear, with just a brief manipulation you can set that power awry. You can later console your subject with a reminder that, after all, nobody's perfect.
A children's choir that I used to sing in always performed the carol "Once in Royal David's City" at a certain concert, and the boy soprano who sang the opening solo would be sent up to a high chapel balcony along with a man who had perfect pitch. The adult would hum the correct note in the boy's ear, apparently, so that he could begin the solo out of a dramatic silence. (Looking back, I'm not sure sending someone up to blow very softly on a pitch pipe wouldn't have accomplished the same thing—but the addition of the superpowered helper made the whole thing more thrilling.)
People with perfect, or absolute, pitch can identify any notes they hear, and can tell you if those notes are a little sharp or flat. Stephen Hedger, a graduate student at the University of Chicago who's studying both cognitive psychology and musicology, has perfect pitch. After discovering that his perception could be skewed distressingly by someone fiddling with a tuning knob while he played the keyboard, he decided to test just how absolute "absolute pitch" really is.
Hedger gathered 13 subjects who'd scored as high as possible on a test of absolute pitch. At the beginning of the experiment, they listened to a series of notes; for each one, subjects had to identify the name of the note and whether it was in tune. The notes included everything from middle C to the B above it, and each note had three versions: one in tune, one slightly flat, and one slightly sharp.
(The out-of-tune notes were off by 33 "cents." The distance between any two notes, say C to C#, is 100 cents. Most people can detect a difference of just 25 cents, so a 33-cent difference—a third of the way to the next note—would be comfortably noticeable to all but the tone-deaf.)
Next, subjects listened to the entirety of Brahms's Symphony No.1 in C minor. During the first movement, which is 15 minutes long, the recording ever so slowly went flat. The pitch crept downward at 2 cents a minute, ending a full 33 cents flat from the original. The remaining half-hour of the symphony was played in the new, flattened key. When asked, none of the subjects noticed said they noticed a difference in pitch.
In a second experiment, instead of Brahms subjects heard a series of modern musical compositions that only include 5 pitches. Just as before, the music slowly drifted flat and then stayed that way. In the pitch quiz afterward, subjects misjudged all the flat and in-tune notes they heard—not only the five notes they'd listened to.
A brief time listening to out-of-tune notes was able to skew a person's whole internal scale. Yet when subjects heard test pitches played by an instrument they hadn't listened to during the experiment—for example, a set of piano notes after the Brahms symphony, which didn't include a piano—their judgements were correct again. It is "as if each instrument voice retains its own tuning," Hedger and his coauthors write in Psychological Science.
People with absolute pitch, those superpowered few, are thought to learn their pitches in childhood. The pitches aren't absolutely stable, though: the detuning study shows they can be bent and changed by music a person has recently heard.
In a video, senior study author Howard Nusbaum says that the group is now looking for ways to improve people's sense of pitch, rather than detuning it, by taking advantage of this flexibility. "We are constantly changing to meet the circumstances around us," he says. That means someday the rest of us may be a little more perfect. Image: by Timothy Valentine (via Flickr) Hedger, S., Heald, S., & Nusbaum, H. (2013). Absolute Pitch May Not Be So Absolute Psychological Science DOI: 10.1177/0956797612473310