Aalborg University Esbjerg, Esbjerg, Denmark, 26-29 May 2004.
Reviewed by Marcus Pearce and David Meredith
London, UK
Introduction
The Second International Symposium on Computer Music Modeling and Retrieval
(CMMR 2004) was held at Aalborg University Esbjerg on the southwest coast
of Denmark on May 26–29, 2004. The symposium was chaired in an effective
but informal style by Uffe Kock Wiil, with Stefania Serafin responsible
for the proceedings, and Richard Kronland-Martinet chair of the program
committee. Mr. Wiil and Ms. Serafin are both of Aalborg University Esbjerg,
while Mr. Kronland-Martinet is at the Centre National de la Recherche
Scientifique, Laboratoire de Mécanique et d'Acoustique (CNRS-LMA),
Marseille, France.
The goal of this symposium series is to provide an opportunity
to meet and interact with peers concerned with the cross-influence of
the technological and the creative in computer music. The interdisciplinary
nature of the field was reflected in the organization of the conference
into session topics in areas such as the synthesis of instrument timbres,
music analysis, music information retrieval, and computer music composition.
This diversity was also reflected in the opening and closing keynote speeches
given, respectively, by Cort Lippe (State University of NewYork at Buffalo),
who spoke about tools for real-time interaction of traditional and computer
instrumentalists, and Marc Leman, who summarized some of the research
carried out at the Institute for Psychoacoustics and Electronic Music
at the University of Ghent in Belgium.
Over three days, 25 paper presentations were made, and
the limit of 20 pages for each meant that the conference proceedings (to
be published in the Springer Lecture Notes in Computer Science series)
are generally reasonably complete in their presentation of background
and discussion of results. To complement the technical presentations in
the conference sessions, CMMR 2004 also included a panel session on computer
music composition and three concerts of computer music.
Music Information Retrieval
One recurring issue which arose during the conference was how to define
a “ground truth” for the evaluation of proposed measures of
perceived musical features. Many of the presentations at CMMR 2004 concerned
the development of systems and techniques for Music Information Retrieval
(MIR), and in this context, Stephan Baumann from the German Research Centre
for Artificial Intelligence illustrated one method of obtaining a ground
truth. The presentation concerned a system for musical artist recommendation
based on clustering using Self-Organising Maps of artist reviews obtained
from the Amazon Web site. The improved quality of recommendations using
a modified scheme for weighting terms extracted from the reviews was demonstrated
by comparing matches between the recommendations of the presented system
with those of another system based on user playlists.
Music Analysis
Another topic represented at the conference was music analysis where the
ground truth is often indicated in the score. For example, Elaine Chew
from the University of Southern California presented work on separating
voices in symbolic representations of polyphonic music. The approach described
depends on assumptions derived from David Huron’s perceptual principles
for voice leading. First, a piece is segmented into "contigs"
at boundary points where the number of voices changes. In a second stage,
starting from contigs with the maximal number of voices present, fragments
in adjacent contigs are ordered by pitch height and reconnected according
to pitch proximity. The implemented algorithm was tested on contrapuntal
music composed by J. S. Bach and yielded promising results.
Other presentations were concerned with the analysis of performances
rather than compositions. Maarten Grachten from Pompeu Fabra University
in Barcelona, for example, gave an interesting presentation on the automatic
annotation of live jazz saxophone performances. This approach uses edit
operations such as insertion, deletion, consolidation, fragmentation,
and transformation according to a cost function parameterized to control
the influence of pitch, duration, and onset for each of the edit operations.
An evolutionary approach was adopted for optimizing the parameter values
for test sets of hand annotated performances. While the solutions significantly
improved the annotation performance over random parameter settings, the
solutions obtained did not converge to a single optimum across disjoint
test sets.
Sound Synthesis and Timbre
As well as research concerning symbolic representations of music, many
of the presentations at CMMR 2004 were concerned with the processing and
manipulation of digital audio. One strand of this research concerned sound
synthesis and the modeling of instrument timbre. Julien Bensa, from the
Université Pierre et Marie Curie in Paris, presented a cognitive
approach to modeling piano timbre. The goal of this research was to associate
objective parameters of acoustic synthesis models of piano timbre with
subjective experiential descriptions obtained in a free association task
carried out with pianists. In another presentation, Phillipe Guillemain,
from CNRS-LMA, analyzed the relationship between two control parameters
of a physical model of the clarinet (blowing pressure and reed aperture)
and four objective timbre descriptors of the generated audio signal. Both
of these presentations were concerned with the association of intuitively
meaningful domains (e.g., natural language descriptions of sound and physical
properties of instruments) with low level audio descriptors. In his keynote
speech, Marc Leman also discussed the problem of associating subjectively
perceived musical qualities with objective acoustic descriptors of audio
signals in the context of MIR.
Audio-to-Score Transcription and Feature Extraction
One topic represented strongly at CMMR 2004 was audio-to-score transcription
and, in particular, the extraction of features for MIR. Indeed, about
a third of the papers presented were concerned in one way or another with
the extraction of perceived structure from musical audio signals. Rui
Paiva, from the Universidade de Coimbra, Portugal, presented a method
for extracting the melody from a polyphonic musical audio signal based
on a model of the cochlea. Meinard Müller described a system developed
at the University of Bonn, Germany, which automatically synchronizes a
score or MIDI file of a work with an audio file. The system works by matching
the source MIDI file with another MIDI file extracted from the waveform
data using novelty curves for note onset detection and multi-rate filter
banks in combination with note templates for pitch extraction. Kristoffer
Jensen, from the University of Copenhagen, Denmark, also used a novelty
measure, in this case extracted from a self-similarity matrix calculated
from a beat histogram ("rhythmogram"), to automatically identify
segment boundaries in rock and techno music.
A Dichotomy between "Composers" and
"Scientists"
Another theme of the conference was the perceived cultural and methodological
dichotomy between "composers" and "scientists." The
"composers" seemed to be far more sensitive to this dichotomy
than the "scientists". One of the 90-minute sessions was devoted
to an open panel discussion of this issue, chaired by the composer Lars
Graugaard (Aalborg University Esbjerg). Cort Lippe opened the discussion
by proposing that today's electroacoustic composers are parasites who
derive their techniques from the results of research in fields such as
signal processing. Harvey Thornburg (Center for Computer Research in Music
and Acoustics, Stanford University, USA) responded to this by claiming
that he had on several occasions been motivated by the creative needs
of composers to develop new signal processing techniques. Two of the panelists,
Juraj Kojs (a composer from the University of Virginia, USA) and Stefania
Serafin, insisted that their collaborative relationship was definitely
symbiotic rather than parasitic.
David Meredith (City University, London) then asked the panel whether
they ever found that their creativity was paralyzed rather than enhanced
by the almost limitless power of the computer-based tools available to
them which essentially afforded an infinite template of possibilities.
Leonello Tarabella (Consiglio Nazionale delle Ricerche, Pisa) suggested
that someone who is bewildered by the technology should probably not be
engaged in computer-based composition! Lars Graugaard explained that he
avoided this problem by always being motivated in his compositions by
an initial idea of the sound structure that he desired which he would
then attempt to realize using technology.
Conclusions
The conference attendance of CMMR 2004 was relatively small, consisting
of not many more than the sum total of the conference organizers and those
presenting or performing. This prompts one to ask whether there is a need
for another conference on the computational modeling of music. Conferences
such as DAFX (International Conference on Digital Audio Effects) cover
the signal processing end of the research field, ISMIR (International
Symposium on Music Information Retrieval) covers engineering approaches
and practical applications such as MIR, ICMC (International Computer Music
Conference) covers computer music, ICMPC (International Conference on
Music Perception and Cognition) covers cognitive modeling of music, and
ICMAI (International Conference on Music and Artificial Intelligence)
covers the abstract modeling of music.
Perhaps the only criticism of CMMR 2004 in terms of its scope is that
it tended strongly towards the practical rather than the theoretical end
of the spectrum. However, possibly because of its small size, the atmosphere
at CMMR 2004 was particularly relaxed and friendly and the interdisciplinary
research presented prompted interesting discussion from a range of different
viewpoints. If the bias toward practical applications could be redressed
by the inclusion of more theoretical modeling and cognitive scientific
research, CMMR would fill a niche as an intimate forum for the presentation
of interdisciplinary research in modeling music.
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