The results suggest that tones above 6 kHz can elicit a salient pitch, sufficient for melody recognition, when they combine to form a harmonic complex tone with a lower F0 (in this case between 1 and 2 kHz). A less interesting interpretation would be that the components are at least partly unresolved and that listeners are sensitivity to the waveform (or temporal envelope) repetition rate of between 1 and 2 kHz, rather than to the individual frequencies. This explanation was unlikely because the tones were presented in random phase, which weakens envelope cues, and because the repetition rates were so high (1–2 kHz) that sensitivity to envelope pitch was expected to be very poor (Carlyon and Deeks 2002). Indeed, two control conditions (run with new groups of six subjects), involving shifted harmonics and dichotic presentation, produced results consistent with predictions based on the processing of individual components, rather than the temporal envelope: when the harmonics were shifted to produce inharmonic complexes but with an unchanged temporal envelope rate, performance dropped to near-chance levels of about 55 %. On the other hand, when the harmonics were presented to opposite ears, performance remained high and not significantly different from that for the original (dichotic) condition. Overall, the results are not consistent with the previously defined “existence region” of pitch (Ritsma 1962). The results also highlight an interesting dissociation, whereby high-frequency tones, which alone do not induce a salient pitch, combine within a complex tone to elicit a salient pitch.

There are different possible explanations for why a dissociation in pitch salience is observed between high-frequency pure tones and complex tones. One possible explanation is that the upper limit for perceiving melodic pitch is determined at a level higher than the auditory nerve, perhaps due to lack of exposure to high (>4 kHz) F0s in normal acoustic environments. Thus, when individual high-frequency tones are presented, they elicit a pitch beyond the “existence region” of melodic pitch. However, when the high-frequency tones are presented in combination with other harmonically related tones, they elicit a pitch corresponding to the F0, which falls within the “existence region.”

Another explanation is that the limits of melodic pitch perception are determined peripherally and that multiple components elicit a more salient pitch simply due to a combination of multiple independent information sources. Based on the results from lower frequencies, this explanation seems less likely: little or no improvement in pitch discrimination is found when comparing the results from individual pure tones with the results from a complex tone comprised of those same pure tones (Faulkner 1985; Goldstein 1973). However, similar measurements have not been made at high frequencies, so it is unclear whether a similar pattern of results would be observed.