The role of spectral-envelope characteristics in perceptual blending of wind-instrument sounds

Certain combinations of musical instruments lead to perceptually more blended timbres than others. Orchestration commonly seeks these combinations and can benefit from generalized acoustical descriptions of perceptually relevant features that allow the prediction of blend. Previous research on correlating such instrument-specific features with the perception of blend shows an important role of spectral-envelope characteristics, leaving unanswered, however, whether global or local characteristics are more important (e.g., spectral centroid or formant structure). This paper reports how wind instruments can be characterized through pitch-generalized spectral-envelope descriptions that exhibit their formant structure and how this is represented in an auditory model. Two experiments employing blend-production and blend-rating tasks study the perceptual relevance of formants to blend, involving dyads of a recorded instrument sound and a parametrically varied synthesized sound. Frequency relationships between formants influence blend critically, as does the degree of formant prominence. In addition, multiple linear regression relying primarily on local spectral-envelope characteristics explains 87% of the variance in blend ratings. A perceptual model for the contribution of spectral characteristics to perceived blend is proposed.