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Terhardt's theory and the tritone paradox
Richard Parncutt's tutorial on Terhardt's model is very instructive,
but the model really explains only the basic pitch class effect--why people
hear some tritone pairs as ascending and others as descending in pitch.
When it comes to explaining cross-language differences, the explanation is
as vague as Deutsch's. There is a difference: Deutsch (as far as I can tell
from her very vague statements) appeals to variations in voice pitch,
whereas Richard's interpretation of what Terhardt meant is that it relates
to vowel formants and the like. What is not clear to me, however, is how
the auditory system could get shaped by exposure to the multitude of
speech sounds generated by vocal tracts of all sizes. The idea seems
appealing, but the mechanism is quite opaque. And until this mechanism
is clarified, the proposed explanation is merely a description pushed
up one level (i.e., from the actual behavior to the hypothetical spectral
Richard also neglects to mention that, in my study, I found strong
effects of spectral envelope for many listeners. This result is indeed
atypical compared to what Deutsch and Pollack reported, and also with
respect to Terhardt's model, but it is a finding in need of explanation.
Apparently, spectral envelope effects do surface under certain conditions,
and the Terhardt model does not allow for that. Mark Pitt (in a personal
communication related to this exchange) has suggested that the effect may
be related to the inability of musically untrained listeners to separate
pitch and timbre--again only in certain situations. This is obviously an
issue of interest to a number of people (Pitt and Crowder, Krumhansl and
Iverson, Demany and Semal, Singh, Moore, etc.). However, my spectral
envelope effect occurred also with musically trained listeners, I believe.
(I did not interview my subjects on that point, but there were several
with musical training among them.)
Finally, how should the finding that I myself do not show a pitch
class effect be interpreted? Do I have a flat spectral weighting function?