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Re: multidimensional scaling of timbre



Hello,

I see at least three possible factors that might contribute to a low dimensionality of multidimensional scaling (MDS) spaces for musical timbres:

1. limited cognitive resources (e.g., attention);
2. noise in the neural representation of stimuli or in the selection/emission of the response;
3. biases of model selection processes for MDS, which might favor solutions with a low number of dimensions.


With the available empirical data, it is, in my opinion, not possible to tell apart these factors.

I might also add that even if a researcher found, say, a six-dimensional MDS space, he would think twice before asking reviewers to get confused with such a "complicated" statistical model: they might just reject the manuscript.

This said, I would like to comment on the two/three-dimensionality of musical timbre.

The general impression that the literature on the topic gives is, indeed, that musical timbre is basically spectral centroid + attack time plus some spurious dimension.

My personal opinion: this view is limited.

If this view was correct, we could make useless centuries of work on the design of musical artifacts by creating an instrument that allows control of large variations in:

1. duration
2. loudness
3. pitch
4. spectral centroid
5. attack time

I have the impression that even if one such instrument could cover the entire musical range for each of these five factors, it wouldn't be able to reproduce the entire palette of musical sounds.

In a nutshell, a 2/3D view of timbre is in stark contrast with the variety of subjective musical experiences I personally have.

Maybe I have this opinion because my playlists go also beyond classical music, whereas the majority of timbre studies focus on classical acoustical instruments ;-)


Best,

	Bruno


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Bruno L. Giordano, Ph.D. Music Perception and Cognition Laboratory CIRMMT http://www.cirmmt.mcgill.ca/ Schulich School of Music, McGill University 555 Sherbrooke Street West Montréal, QC H3A 1E3 Canada http://www.music.mcgill.ca/~bruno



Christian Stilp wrote:
This is true across a wide array of studies, from those of John Grey and David Wessel in the 1970s to more contemporary investigations of Stephen McAdams, Carol Krumhansl, Suzanne Winsberg, and others in the 1990s and 2000s. Furthermore, two of the primary dimensions of musical instruments in these tasks include the temporal envelope (rise time, or attack) and spectral envelope (centroid, center of gravity, energy distribution, "flow", etc.). Those two dimensions seem sufficient to organize any set of instruments, no matter how diverse (e.g. different spectral characteristics across all classes of instruments, or just subdividing the woodwinds). While tertiary and beyond dimensions uncover some interesting ideas (spectral flux, attentuation of even harmonics, "richness", spectral irregularity, f0 intensity, inharmonic energy in the attack, etc.), their sparseness in timbre MDS literature suggests they are more artifacts of the particular instruments at test.

Cheers,
-Christian Stilp

Christian Kaernbach wrote:
Dear list,

I seem to remember that one lesson from multidimensional scaling of timbres was that the type of dimensions found depends strongly on the selection of the stimuli. If my memory serves me right, the similarity data would alway yield two- to three-dimensional spaces, regardless of whether the stimuli were quite divers (all types of instruments of the classical orchestra) or from a narrow subgroup (say, all woodwinds). In other words, people seem to be able to manage two to three dimensions in their cognitive space representing the entirety of the stimuli of a certain experiment. Is that correct, and is there a reference referring to this phenomenon?

Thanks in advance,
Chris