The Making of "Wildlife"
David A. Jaffe and W. Andrew
Schloss
D. A. Jaffe, Box 4268 Stanford, CA 94309 USA
email: daj@ccrma.stanford.edu
W. A. Schloss, School of Music, University of
Victoria, Victoria BC CANADA V8W 2Y2
email: aschloss@nero.uvic.ca
This paper describes some of the issues that came
up in the composition of Wildlife, an improvisationally-oriented interactive computer piece. We address the question of what makes a
good "machine partner" and how the duo ensemble situation can be
expanded by the use of configurable instruments and computers.
Introduction
Wildlife is a computer-extended duo in five movements for
Mathews/Boie Radio Drum and Zeta violin.
It was co-composed by Jaffe and Schloss and was premiered by the
composers in Victoria, Canada in 1991.
It has been performed numerous times in North America and Europe and is
planned to be released on an upcoming CDCM compact disc of music featuring the
Radio Drum.
The name
"Wildlife" is used in two senses. First, it refers to the improvisational nature of the
work. All materials are generated
in direct response to the performers' actions and there are no pre-recorded or
stored sequences. Furthermore, the
malleable nature of the instruments allows the traditional boundaries that separate
one instrument from another to be broken down. As a simple example, the violinist's glissando may change
the pitch of chords played by the percussionist. Allowing the computer a degree of autonomy takes the
performers a further step away from the customary ensemble relationship. Thus, they find themselves "living
on the wild side."
The autonomy provided the
computers gives rise to the second sense in which the name "Wildlife"
applies. Robotic expert Hans
Moravec describes, in his recent work Mind Children, a world in which
autonomous artificial life forms breed, propagate, compete and interact. These life forms can be
beneficial, parasitic or benign.
In Wildlife, the computers
spawn independent processes that suggest such beings.
Technical Description
The Mathews/Boie Radio Drum
is a sensor capable of reporting accurately the position of two mallets in
three dimensions. It generates no
sound; the effect of a performed gesture is entirely determined by software. The Zeta violin is a solid-body
electric violin with both a MIDI output and an amplified electronic sound. Each string has its own pickup and
pitch detector, allowing for independent pitch bend for each string.
The system configuration
consists of both the Zeta violin and the Drum passing information to a
Macintosh IIci computer, which does preliminary gestural processing and passes
MIDI information to a SampleCell sample player and a NeXT computer. The NeXT does
further gestural processing and algorithmic music generation, performs
synthesis on the NeXT's built-in DSP chip, and sends MIDI to a Yamaha TG77
synthesizer. The software on the
Macintosh is based on the Max system, while the software on the NeXT is based
on Ensemble and the NeXT Music Kit.
In addition to the Radio
Drum and the Zeta violin, both performers have a number of foot pedals and
switches. Of particular interest
is the percussionist's 18-key chromatic bank of organ-style velocity-sensitive
foot pedals. These pedals are used
for numerous kinds of control information rather than playing pitches, however,
we have found that the standard "black and white key" orientation
facilitates locating the
footswitches quickly and easily.
Plan of Attack
We began work on the piece
by exploring a wide range of interactive scenarios. We quickly found that many were unsatisfactory for various
reasons. In particular, as
improvising performers, we found it essential to feel that our actions had a
discernable and significant effect on the music being produced. In many situations, one or the other of
us felt that his influence was inconsequential. The situation was analogous to playing a solo in a jazz
ensemble with insensitive accompanists.
The manner in which we felt we needed to be able to exert influence
could be very different for each of us in a given situation. Yet, there was definitely an
intangible but undeniable difference between those situations where we felt our
improvisational imagination was fired and those where we felt it inhibited by
opaque complexity.
Visceral Learning
It was difficult to predict
whether or not an interactive scenario imagined on paper would turn out to be
effective in performance. The only
way we could decide what worked well was by long hours performing with each
setup, searching for material that seemed to complement it, and exploring its
potential. Though we both
understood fully the logic being executed by the computer programs, it was only
by exploration as performers that we discovered hidden aspects. Thus, the music for each of the five
movements was developed in parallel with the interaction scheme.
As a simple example, in the
fourth movement, the violinist supplies the pitches that make up the
percussionist's improvisation. The
percussionist can choose to play recently-played pitches or can go back in time
to pitches played earlier. In this
context, the violinist plays only
occasionally and in such a manner as to change the flow of the ongoing music. This movement was particularly
difficult for him because the effect of material he played was evident only
some time later when the percussionist played these pitches. Yet, an implementation detail turned
out to supply the answer. It turns
out that the "remembered" pitches played by the violinist are stored
in a buffer which is not circular.
Thus, every hundred notes (this number was at first set arbitrarily),
the buffer would be empty and would start to be refilled again. This quirk turned out to provide just
the "foot in the door" that the violinist needed. By playing tremolo, he could fill up
the whole buffer with a single pitch and constrain the percussionist to that
pitch. The implementation
also guaranteed that every now and then the percussionist would be forced to
play only very-recently performed pitches. Thus, what started out as an arbitrary
irrelevant constraint turned out to be an asset in disguise. "It's not a bug it's a
feature!"
Musical Cowboys
When we gave the computer a
large degree of autonomy, the major problem became how to avoid the feeling the
music was "getting away from us." One way to deal with this problem is to consider the
performer's role as analogous to that of a conductor of a piece that doesn't
use strict rhythmic coordination between parts. In such a piece, the conductor gives signals that control
the large-scale flow of the music, but without specifying the individual
details. To use a more colorful
analogy, the independent computer processes are like cattle that are allowed to
wander over the open plains and the performer's control is that of the cowboy
who reigns them in when it's time to go into the corral.
As an example, in the third
movement, the computer is generating melodic material based on the pitches
played by the violinist, but transposing those pitches to any octave and using
fractal shapes to derive melodic, rhythmic and dynamic contours. The percussionist can exert control
over this process by changing the upper and lower range of the computer
process, by changing whether or not repeated notes are tied, and by changing
the tempo. The computer process
also can be made to follow players' dynamics. The violinist can change the density of the computer process
by playing repeated notes. Thus,
the computer processes can be allowed to wander freely and then be reigned in
suddenly in response to the performer's
actions. Nevertheless, the process is interesting and complex enough
that the computer often seems to have a mind of its own. We are never sure how it is going to
behave and are often surprised (and sometimes perplexed) by its seeming whimsy.
Crossing Boundaries
Traditional instruments have
clear boundaries. They may play in unison, combining to produce a new timbre;
they may combine harmonically or contrapuntally. But each performer is in control of the sound produced by
his instrument and is the sole determiner of the notes he will play and when he
will play them. In contrast, with
"virtual instruments" (controllers) like the Radio Drum and
controller-instrument hybrids like the Zeta Violin, the traditional boundaries
between performers can become like permeable membranes. As a simple example, the violinist's
glissando can change the pitch of notes produced by the percussionist and the
percussionist can control the loudness of the electric violin sound. This situation is analogous to the
humorous trick performed by bluegrass bands in which the guitarist reaches his
left arm around the banjo player and plays the chords of the banjo while the
banjo player does the picking, and at the same time, the banjo player reaches
his left arm around the guitarist's back and plays the chords for his
instrument.
The crossing of boundaries
can happen on a larger formal level as well. In the fifth movement, the percussionist plays arpeggiated
consonant chords. The root of each
chord can be specified by either the percussionist or the violinist. The violinist specifies the root
by stepping on a pedal. The next
note he plays sets the new root.
If he uses the pedal only occasionally, the harmony changes slowly and
is consonant. However, if he uses
the pedal frequently, on every note for example, the effect is much more
complex and dissonant. Since the
percussionists' chords are transposed according to the octave of the violin
note, the violinist also has control over the percussionist's range. At the same time, the percussionist has
a similar pedal and can surprise the violinist by changing the harmony out from
under him, but in a way intimately related to what the violinist has just
played. Thus, the harmony emerges
as a result of a complex improvisational interaction.
An Example In Detail
The first movement begins
with a simple interaction scheme, allowing the audience to perceive the
causality between performed action and resulting synthesizer sound. The violin, in addition to its acoustic
sound, produces pitches via a "chord mapping set", defined as twelve
"chord mappings." A
chord mapping is a chord that is produced when a particular pitch class is
performed and transposed in a manner corresponding to the performed
octave. The Drum selects which of
several chord mapping sets is active. As an example, one set might produce
chords derived from chromatic tone clusters while another might produce a
different octave-displacement for each pitch.
The Drum's horizontal axis
controls register, the vertical axis controls duration and the height above the
surface controls loudness. The
surface is also partitioned in half, with one part of the Drum playing chords,
and the other playing single notes.
Overlaying this partition is a grid that the percussionist uses to
select the active chord mapping set.
Thus the familiar gesture of striking the drum can have the unfamiliar
result of changing the harmonization of the violinist's melody, an effect
usually considered in the realm of composition rather than performance.
Another interesting aspect
of this movement from an ensemble standpoint is that both performers are
playing the same synthesized sound at the same time, resulting in ambiguity as
to who does what and enabling one player to "pull the rug out from
under" the other player.
Summary
Our experience with Wildlife
shows that improvisational ensemble
music and interactive instruments can be a powerful combination. The traditional inviolability of a
performer's sole control over his instrument can be relaxed and the degree of
invasion of one performer's control over the other's instrument can be
controllable as a musical parameter.
Adding to this situation semi-autonomous computer processes that the
players can control in the manner of a conductor further enriches the
environment.
However, to discover an
effective interactive scenario, it is necessary to spend a good deal of time
playing with the system and learning its idiosyncrasies. Improvisation is ideal for
allowing this to occur, since it lets the performer react spontaneously to the
musical situation. No amount of
programming skill and cleverness is a substitute for the process of using the
system in a musical context.
Acknowledgements
Thanks to visionary
instrument builders Max Mathews and Bob Boie (Radio Drum) and Keith Mcmillian
(Zeta violin.) Thanks also to
Michael McNabb, whose Ensemble program has been enormously useful in this work,
Julius Smith, who co-developed the NeXT Music Kit with the author, and Miller
Puckette and David Zicarelli, whose Max program proved extremely valuable.
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