A Dynamic Model of Metric Rhythm in Electroacoustic Music
Jeff Morris
Center for Experimental Music & Intermedia, University of North Texas
Jeff.Morris@HBProductions.net
Abstract
The possibilities offered by electronic composition tools,
while liberating, make difficult the dynamic use of
organized rhythm in electroacoustic music. This paper
explores a model stemming from interactive electroacoustic
work by the author that adapts aspects of the hocketed,
disjunct rhythmic textures of funk styles for use as a
developmental musical parameter. These methods for
generating rhythm that facilitate transformation in ways
more naturally manipulated by computer-based tools are
demonstrated in theory and in use by the author.
1 Introduction
Modern electronic tools for music composition allow a
practically infinite variety of time relationships; however,
this freedom has made it difficult to organize rhythm as an
active developmental parameter of a musical work. Most
tools either leave composers adrift in a practical continuum,
or force them to wrestle with (or settle for) conventional
eighteenth-century metric patterns. A common solution is to
use a multitrack audio production tool that allows metric
grids to be placed over a temporal continuum. It is possible
for multiple sounds to be organized according to different
metric grids, but each grid is static, is limited to
conventional meters, and makes for tedious work placing
each sound. After bouncing a static rhythmic passage to a
single file, a phase vocoder or granular sampling application
could be used to warp the rhythm in controlled ways, but the
attack envelope of the sounds would be distorted as well.
Some applications offer a tempo map in which time can be
warped without distorting the original sounds, but these
tools can usually only support one (conventional) meter at a
time and still require tedious placement of individual
sounds. As one alternative to these limitations on rhythmic
organization and development, the model presented here,
developed in the Max/MSP programming environment,
gives unique dimensions of flexibility and structure in
electronic or acoustic algorithmic composition, in or out of
real-time.
2 Theory
This work was inspired by attempts to describe the
principles active in musical moments that are
simultaneously engaging and elusive, the combination of
which evokes a special excitement in the listener. This
seems to be mainly the realm of rhythm and texture, and is a
key element of funk styles. The effect is achieved through a
kind of balance between predictability and surprise, such
that a listener is compelled to follow, despite being
continually shaken loose. This is related to musical
discussions of entropy (in the form of surprise; Meyer
1967): the balance is somewhere between redundant stasis
and continuous change. When achieved, the effect is
synergistic, as if the stimulus were much more complicated
that it actually is and more exciting than the simple sum of
its components. The term tickle is used here to refer to this
effect of engaging elusiveness.
Study of funk metric structures has revealed that the
music is usually unstable at the level of the single 4/4
measure, but stable at the levels of the eighth note pulse and
the two-measure segment. Whereas the former is more
widely recognized, the stability of the two-measure segment
comes from a tendency to disrupt every second downbeat
(usually by delay or anticipation). One measure often does
not look like the next measure, but one pair of measures is
often very similar to the following pair. Between these
stable levels is where the tickle is evoked. The quarter note
beat is usually unstable; the steady eighth note pulses are
divided into groups of two or three by accents. It is in the
mixture of two- and three-pulse groupings that elements of
stability and surprise can be manipulated. This is congruent
with studies demonstrating that human perception is most
sensitive to a specific range of durations, peaking around
one half second (Fraisse 1963, Povel 1981). It appears that
the ticklish component must be focused within this range to
be effective and that it needs stability on adjacent levels to
react against.
pulse groups
2 2 3 2 2 1 3 ' 2
Figure 1. The guitar riff from James Brown's "Give It Up or
Turnit A Loose" (1968/1996) demonstrates an accent
pattern of 2, 2, 3, 2, 2, 3, 2. Note how a pulse group lies
across the barline.
Proceedings ICMC 2004
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