- ...perception
- Our main results were presented at the May 1992 meeting of the Acoustical Society of America, Salt Lake City
(see Chaloupka et al (1992))
- ...cents
- The width of an interval between tones of frequencies
and 
in cents
is defined as a logarithm of the frequency ratio:
For an absolute pitch in cents used in mode 1 (Figs. 2 and 5), we arbitrarily used a reference frequency
Hz. For mode 2
(Fig. 3), we use 
Hz.
- ...laboratory
- The standard deviation of the distribution of the difference
between the request and the response of our subject was about 30 cents
(see Fig. 3 and Fig. 4 for the results from the two ``active modes", and Fig. 6c
for quantitative results from the ``passive" mode). In terms of categorized ``note identification", this translates into KR identifying semitones with
accuracy, and is well within the considerable range of
accuracies of absolute pitch possessors reported in the literature. This, and the practically instantaneous and
effortless performance appear consistent with the "genuine absolute pitch" as defined by Bachem (1955).
- ...caution
- There is large variability in the ``normal" perception profile from subject to subject (see Sundberg and Lundquist (1972), and references quoted therein). Comparison with the literature, and measurements on other subjects
using methods described in the present study, indicate that most subjects
exhibit somewhat larger octave stretching than that found for our subject when not under the influence of the drug.
For the most recent investigation of the phenomenon of octave stretching see Hartmann (1993).
- ...same
- The phenomenon of absolute pitch is often associated with the concept of ``chroma" introduced by Bachem (1937)
(``...the general term `tone chroma' shall point to the underlying quality of any tone and the tones in octave periodicity with it.").
As summarized more recently by Balzano (1984): ``... pitch itself consists not only of some monotone mapping of frequency but also
an ensemble of equivalence classes generated by octaves. ... Tone chroma, or pitch class, as musicians call it, is just
as objectively specifiable as frequency, whether or not we currently possess any instruments for measuring it." The problem is that
the ``octave periodicity" is apparently much more subtle than a simple multiplication of frequencies by powers of two. This is illustrated by the phenomenon of octave stretching, and most directly by our data, with the subject associating, in the on-drug and off-drug periods, quite different patterns of frequencies to the same ``pitch classes', with comparable ease, confidence and standard deviation of points about the mean.
It seems that it will not be easy to objectively specify the elusive chroma.
- ...perception
- The time dependence of the ``accuracy" and consistency of absolute pitch was recently investigated e.g. by Wynn (1992a,b).
On a somewhat anecdotal level, many absolute pitch possessors report that after the age of 40 - 50, they hear tones as being one or even two
semi-tones higher than the correct pitch. For references to some of these reports see Ward and Burns (1982).
On an even more anecdotal level, there are many reports of pitch shifts due to ``simply clenching one's jaw".
- ...perception
- In a very interesting paper on absolute pitch (and IQ scores!) before and after brain surgery, Zatorre (1989) remarks:
``There are also indications (Tanzman, personal communication; Zatorre, unpublished observations), that some subjects with
A(bsolute) P(itch) experience an alteration in their pitch perception when taking Tegretol .."
We thank E.M.Burns for bringing this reference to our attention.