ShepardTone

Computes a Shepard tone which consists of a superposition of sine waves separated by octaves.

For the description, I took the abstract of the original publication:
"A special set of computer-generated complex tones is shown to lead to a complete breakdown of transitivity in judgments of relative pitch. Indeed, the tones can be represented as equally spaced points around a circle in such a way that the clockwise neighbor of each tone is judged higher in pitch while the counterclockwise neighbor is judged lower in pitch. Diametrically opposed tones -- though clearly different in pitch -- are quite ambiguous as to the direction of the difference. The results demonstrate the operation of a "proximity principle" for the continuum of frequency and sugges that perceived pitch cannot be adequately represented by a purely rectilinear scale." (Shepard, R.(1964) "Circularity in Judgements of Relative Pitch". Journal of the Acoustical Society of America 36 (12): 2346-53.)