Pitch variation is unnecessary (and sometimes insufficient) for the formation of auditory objects.

Kubovy and Van Valkenburg (2001) have posited a theory of auditory “objecthood” that draws heavily on a proposed analogy between the auditory and visual systems. Specifically, they have suggested that the auditory dimension of pitch is analogous to the visual dimension of spatial extent and that pitch is an “indispensable attribute” in the formation of auditory objects. In their development of an auditory “Theory of Indispensable Attributes” they propose that variation in pitch is a necessary and sufficient condition for the perception of auditory figure-ground relationships and thus for the perception of “auditory objects”. In this paper evidence is presented that suggests that differences in pitch are unnecessary for the formation of auditory objects and that under some circumstances, pitch differences are insufficient for the formation of auditory objects.