In psychoacoustics, pitch scales have received less attention than other aspects of pitch perception. Pure-tone frequency discrimination is one task that has been used to assess the accuracy of peopleÕs pitch perception. On each trial, the listener receives a warning that the trial is starting, then hears two ÒintervalsÓ. The signal occurs in one, but not in the other, randomly. The listener chooses the interval that contained the higher tone, and the difference between the two tones in frequency, ÆF, can be manipulated to find a threshold.