General and Biological Psychology: Emotion and Oscillation Lab


The pitch helix describes two aspects of pitch: absolute pitch height, and chroma. When using complex tones with octave related harmonics under a special amplitude envelope, so-called Shepard tones, the height dimension becomes perceptually ambiguous and the helix collapses into a circular pitch configuration: chroma. If the elements of the chroma circle are played in close succession one after the other, the impression of an endlessly ascending scale can be created which at the same time does not seem to get any higher in pitch at all. We examine different ambiguities associated with these stimuli and try to describe them with perceptual models and to identify influences of language and language acquisition.

Animated demonstration of the pitch helix for simple sine tones with unambiguous pitch height and for Shepard tones