Musical timbre beyond a single note: tessitura and context
Roger A. Kendall
The majority of research in timbre has involved a single note drawn from the middle range of the group of instruments studied. A common finding among such studies is a strong mapping (r>.89) between long-time-average spectral centroid (spectral center of gravity) and the principle dimension in multidimensional scaling analysis of perceptual similarities when continuant steady-states are considered. Another acoustical variable, often mapping to the second dimension, is spectral flux or varaiability. In fact, it has been shown that when synthetic emulations of instruments fail to capture these two variables, their similarity to natural instruments suffers (Kendall, Carterette, Hajda, 1999).
The present study extends previous research by exploring the patterning of spectral centroid across the playing ranges of orchestral instruments. A concert Bb scale consisting of quarter notes followed by a quarter reset (M. M. = 72) was recorded across the playing ranges of a large set of wind and stringed instruments. In addition, the melody "All Through the Night" in Bb was also recorded in the middle tessitura. Spectral analyses were conducted for every steady state (ca. 1000 msec) across these performed contexts, and the unweighted spectral centroid (indpendent of frequency) calculated. Various comprative statistical analyses of these physical data were conducted. Next, resynthesis was employed with an average spectral centroid across the tessitura of the instrument applied without variance to every note of both the scale and melody. In addition, the lowest concert Bb centroid was applied, as well as the highest concert Bb applied. Perceptual similarity and verbal ratings of timbral quality were conducted within instrument across these independent variables. Results are too complicated to present here, and analysis continues.
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