6
THE ROOTS OF MUSICAL
VARIATION IN PERCEPTUAL
SIMILARITY AND
INVARIANCE
c
Abstract
Perceptual similarity underlies a number of important psychological properties of musical materials
including perceptual invariance under transformation, categorization, recognition, and the sense
of familiarity. Mental processes involved in the perception of musical similarity may be an integral
part of the functional logic of music composition and thus underly important aspects of musical
experience. How much and in what ways can musical materials be varied and still be considered as
perceptually related or as belonging to the same category? The notions of musical material, musical
variation, perceptual similarity and invariance, and form-bearing dimensions are considered in this
light. Recent work on similarity perception has demonstrated that the transformation space for a
given musical material is limited by several factors ranging from degree of match of the values of
auditory attributes of the events composing the sequences, to their relations at various levels of
abstraction, and to the degree that the transformation respects the grammar of the musical system
within which the material was composed. These notions and results are considered in the light of
future directions of research, particularly concerning the role of similarity and invariance in the
understanding of musical form during listening.
Keywords:Similarity in music; Invariance in music; Musical variation; Perception of music
Introduction
Perceptual similarity underlies a number of important psychological properties of musical
materials including perceptual invariance under transformation, categorization, recogni-
tion, and the sense of familiarity. Mental processes involved in the perception of musical
similarity may be an integral part of the functional logic of music composition and may thus
underly important aspects of musical experience. We are interested in the perception of
musical materials and of their musical transformations, that is, ‘themes’ and ‘variations’ but
in a much larger sense than is usually attached to this specific form in Western tonal music.
A longer term goal of this approach is to understand the role of the perception of
similarity and invariance, as well as that of the change produced by variations of the