Effects of frequency and amplitude modulation on the pitch of a complex tone with a mistuned harmonic.

It has previously been found that when a single low-numbered harmonic of a complex tone is progressively mistuned, for mistunings up to about 3%, the pitch of the complex changes in the direction of the mistuning but for larger mistunings (by about 8%) the pitch returns to its original value. This result is compatible with the operation of a mechanism such as a graded harmonic sieve, which can reject from the calculation of pitch those frequency components that are implausibly distant from a harmonic frequency. The first experiment shows that the tolerance of such a sieve is increased when all the components of the complex tone (including the mistuned component) share a common pattern of frequency modulation at a rate of 6 Hz. The second experiment shows that the tolerance of the sieve is not increased when the components share a common pattern of amplitude modulation at 17 Hz. The third experiment replicates these findings and further shows that the increase in sieve tolerance for FM, but not for AM, occurs at both 6 and at 17 Hz.