Re: multidimensional scaling of timbre

["Bruno L. Giordano" <bruno.giordano@xxxxxxxxxxxxxxx>]

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