“Features that happen at or near the same time or are related in other ways are then thought to be correlated and bound into units (see von der Marlsburg, 1996).
These units are auditory events. For instance, when a number of frequencies that are whole- number multiples of each other begin at the same time, a pitch event consisting of overtones is perceived.
This simultaneous auditory grouping binds the isolated outputs from separate feature extractors into coherent auditory events.
The purpose of this process is to reconstruct discrete sound events in the world, which usually have several correlated acoustical characteristics that happen simultaneously.
This binding of perceptual features is a basic form of association (see Fuster, 1995: 102; Edelman, 1989: 48; Edelman, 1992: 87–90).
That is, when particular features occur together, the groups of neurons that constitute their feature extractors are 4 thought to communicate with each other (Bharucha, 1999: 425–427).
These con- nected features become a representation of some particular kind of event: a per- ceptual category.
Further occurrences of this kind of event will then be processed through some of these same groups of neurons.
A simplified example of perceptual binding might be combining the change that indicates the beginning of a note with its frequency and its tone color (each extracted by different specialized groups of neurons) to produce the impression of a coherent note starting at a particular time with a particular frequency and tone color.
These note events are the auditory equiv- alent of visual objects, which are also formed from the binding of separate features such as edges, shape, color, and texture.
This formation of coherent auditory events from separate acoustical features is a form of perceptual categorization.
Catego- rization is a grouping together of things into a higher-level unit, and in this sense the binding together of features into a single musical event makes that event a basic auditory category.”