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related by a half-octave (an interval comprised of
six semitones, known as a tritone). The composi-
tion of the tones is such that their note names are
clearly defined, but they are ambiguous with
respect to which octave they are in. So, for exam-
ple, one tone might clearly be a C, but in principle
it could be Middle C, or the C an octave above, or
the C an octave below. So when listeners are asked
to determine whether a pair of such tones forms
an ascending or descending pattern, there is liter-
ally no correct answer. (Tones such as these were
used by Roger Shepard and Jean-Claude Risset to
produce illusions of endlessly ascending scales
10 and glides. )
Surprisingly, when one such tone pair is
played (say, D followed by G#) some listeners
clearly hear an ascending pattern, whereas other
listeners clearly hear a descending one. Yet when a
different tone pair is played (say, F# followed by C)
the first group of listeners now hears a descending
pattern whereas the second group now hears an
ascending one. Furthermore, for any given listener,
the pitch classes generally arrange themselves per-
ceptually with respect to height in a systematic way:
Tones in one region of the pitch class circle are heard as higher and those in the opposite region as lower. This is illustrated in Fig. 2, which displays the judgments made by four different lis-
“if we assume that early in human history absolute pitch developed as a feature of speech, and that the circuitry responsible for its processing can also be applied to musical tones, we have a viable framework for understanding absolute pitch and its characteristics, particularly its rarity in our culture.”
teners. Since their judgments varied systematically depending on the positions of the tones along the pitch class circle, the listeners must have been employing an implicit form of absolute pitch in making these judgments.
It has been found that the way the pitch class circle is ori- ented with respect to height is related to the language or dialect to which the listener has been exposed,11 particular- ly in childhood,12 and also to the pitch range of his or her
12,13
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vocal tract, and so on.
There is other evidence that people
who do not possess absolute pitch as con- ventionally defined nevertheless possess the ability in implicit form. In one study, musically trained listeners were presented with excerpts of Bach preludes, and 30% of those without absolute pitch were able to differentiate the correct version from one
16
18
Such find- ings have led to the conjecture that the implicit form of absolute pitch that is reflected in judgments of the tritone paradox originally evolved to
speaking voice.
This hypothesis is bolstered by find- ings that the pitch range of an individual’s speaking voice is related to his or her linguistic community, and not to physi- ological features such as height, weight, chest size, length of
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sub-serve speech.
that had been pitch-shifted by a semitone. Other research has shown that people without absolute pitch tend to be fairly consistent in the pitches with which they hum or sing familiar songs on different occasions;17 further, when asked to sing a popular song that had been recorded in only one key, they produce pitches that are
close to those in the recorded version. Given the evidence for implicit absolute pitch, the inability of most people to label isolated notes is indeed baffling. The evidence strongly indicates that the problem is not one of long term memory, but is instead related to verbal labeling, and so to speech processing. We shall be exam-
ining this conjecture in detail below.
The genesis of absolute pitch
Given the rarity of absolute pitch, there has been considerable speculation concerning its genesis. One view, which has been championed for over a century,19
Fig. 2. Judgments of the tritone paradox made by four different listeners. To produce this illusion, pairs of tones are played that are in opposite positions along the pitch class circle (see Fig. 1). For example, C is played fol- lowed by F#, or D followed by G#. Listeners judge whether each pair of tones forms an ascending or a descend- ing pattern. The judgments of most listeners vary in an orderly fashion depending on the positions of the tones along the pitch class circle, showing that the listeners employ an implicit form of absolute pitch in making these judgments. (Data taken by the author.)
12 Acoustics Today, October 2006