Categorical Perception

Expressions of Categorical Perception in Pitch and Melody Processing

The existence of intonation and relative pitch skills in trained musicians is a well-documented example of categorical processing of musical pitch. Contrary to absolute pitch possessors, who are able to identify intervals by identifying the pitch class of each tone directly, the majority of musicians need to rely on relative pitch skills to perform any basic music function; the ability to discriminate between intervals is essential even for student musicians. However, despite the fact that trained musicians display extremely high levels of accuracy in judging intervals, they are at the same time able to accommodate equally large variations in pitch, in the form of mistuned notes, during a performance.

When listening to short melodic sequences that have been experimentally manipulated so that some pitches are noticeably mistuned, relative pitch possessors are able to identify the out-of-tune version of the melody as being identical to the original; on the other hand, when pitches are altered above the semitone threshold, musicians perceive those as changes in notation. Moreover, in a performance context, musicians appear to be almost desensitized to intonation changes, in some instances as far as the semitone, while they judge the—technically mistuned—performances as correct; this finding is consistent across music genres and idioms. Such findings suggest that the perception of pitch is mediated by acquired, culturally relevant and task-useful categories, which are used to class whole groups of frequency ranges as equivalent.

Comparison between different music cultures also provides useful insight into pitch perception: Although the existence of microtonal music idioms proves that the interval represented by the semitone does not reflect a physical boundary in intervallic identification accuracy, Western-trained musicians and nonmusicians familiar with the Western musical culture appear unable to detect changes of less than a semitone. The ability to discriminate changes in intonation from changes in pitch, as well as the existence of culturally dictated differences in the determination of musically meaningful intervals, provide strong evidence in support of the categorical processing of musical pitch.

...