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In this part of the chapter you will conduct a replication of Deutsch's Tritone experiment. The purpose of this experiment is for you to experience the effect and to find out how, in your perception, the pitch class circle is oriented for you. As such, there will be considerably fewer trials than would be the case for an actual experiment.
To do a more exact replicatation of the experiment, see Diana Deutsch's CD "Musical Illusions and Paradoxes."
There will be four sets of 12 trials, for a total of 48 trials. Each trial will consist of a pair of tones which are a tritone apart. Once the pair is sounded, your task is to determine whether the second of the two tones goes down from or goes up from the first by pressing the "Down" or "Up" buttons respectively. You will have 4 seconds before the next trial begins. If you find that you can't decide, press either one: this particular pair will reappear three more times, over the course of which your determinations may become more definitive.
After the twelfth trial in a set, there will be a 10 second pause (accompanied with a message appearing on the screen indicating the end of the set) before the next set begins. Once all four sets of trials have sounded, the results will appear on the screen. These results are collected from all four sets of trials; they depict the number of times you responded with "down" for each of the 12 pitch classes. You should see something that looks like this:
According to the data displayed, there c-gb were never heard as descending; neither were db-g, etc. However, eb-a were heard as descending, as were e-bb, f-b, and so on. Those pitch classes that have the higher incidence of being detected as descending go at the top of the pitch class circle, while those with lower rates go at the bottom of the circle: this determines your own orientation with respect to the pitch class circle.