Perceptual and acoustical features of natural and synthetic orchestral instrument tones

Four experiments were conducted to explore the timbres of natural, continua nt orchestral instruments with emulation based on sampling, frequency modul ation (FM) synthesis, and a hybrid consisting of sampling and synthesis tec hniques combined. Identification of instruments using verbal labels was sig nificantly better for the natural and sampling-based signals than for eithe r FM synthesis or the hybrid technique, a result also found for aural categ orization. Perceptual scaling of timbral similarities demonstrated great co nsistency across a series of independent variables, including musical train ing, monophonic and stereo presentation, and long versus short signal durat ions. The first dimension of the classical multidimensional scaling (CMDS) solutions mapped onto long-time-average spectral centroid. The second dimen sion mapped onto a measure of spectral variability. Little evidence was fou nd for the mapping of attack time or signal duration onto either dimension. A third dimension separated most natural instruments from their emulated c ounterparts. Experiments using verbal attribute ratings confirmed the corre lation of spectral centroid, the first dimension of the perceptual space, a nd ratings of nasality; the second dimension correlated with spectral varia bility and modestly correlated with ratings of rich, brilliant, and tremulo us. Mismatches of spectral distribution and variability resulted in poor em ulations of the natural instruments. Results suggest that further study of centroid and time-variant psychophysical properties is warranted.