To study the perceptual structure of musical timbre and the effects of musical training, timbral
dissimilarities of synthesized instrument sounds were rated by professional musicians, amateur
musicians, and nonmusicians. The data were analyzed with an extended version of the
multidimensional scaling algorithm CLASCAL [Winsberg & De Soete, Psychometrika, 58,
315-330, 1993] that estimates the number of latent classes of subjects, the coordinates of each
timbre on common Euclidean dimensions, a specificity value of unique attributes for each timbre,
and a separate weight for each latent class on each of the common dimensions and the set of
specificities. Five latent classes were found for a three-dimensional spatial model with specificities.
Common dimensions were quantified psychophysically in terms of log rise time, spectral centroid,
and degree of spectral variation. The results further suggest that musical timbres possess specific
attributes not accounted for by these shared perceptual dimensions. Weight patterns indicate that
perceptual salience of dimensions and specificities varied across classes. A comparison of class
structure with biographical factors associated with degree of musical training and activity were not
clearly related to the class structure, though musicians gave more precise and coherent judgments
than did nonmusicians and amateurs. The model with latent classes and specificities gave a better fit
to the data and made the acoustic correlates of the common dimensions more interpretable.