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De Erratiese Synkretiseur
(The Errant Syncretizer)
by Aad te Bokkel,
Postbus 781,
2501 CT Den Haag.
0. INTRODUCTION.
Although computers provide good means to
make a musical score, in which it can
interact with a human instrumentalist in
a certain static composition, this idea
never attracted me. On the contrary, I
preferred to investigate possibilities
of using a micro-processor-system as a
musical instrument. Such a system would,
rather than produce musical sounds,
provide more flexible means to control
music than any other conventional
instrument. In this way it seems to be
better to think of a "computer-player"
as a systems manipulator, than as a
musician.
In the recent period working at STEIM in
Amsterdam, I got deeply interested in
what could be achieved with a
minimum-system: a MIDI-controller, a
small micro-computer and a synthesizer.
Learning from George Lewis and Michel
Waisvisz I put together such a system
and with the support of Joel Ryan
started programming it.
This system, which is called "the errant
syncretizer", provides a continuous
stream of voice changes of which speed
and direction are controlled by the
performer during performance.
In this system the synthesizer can be
played by the performer and the errant
syncretizer. The errant syncretizer
listens continually to the music,
interprets rhythm and melodies and
reacts to what is played on basis of
what is played before. The performer can
continuously slow down and speed up
tempo, without stopping the program from
accurately detecting rhythm, although
the errant syncretizer can audibly doubt
("switch" to and fro possibilities) when
confronted with an amphibolic situation.
In this paper I would like to describe
the errant syncretizer and how the
MIDI-controller (at present a DX7) is
used as a system-controller. Further is
explained what programming techniques
are used to create an operating
environment based on event-manipulation,
in which most events are described by
MIDI-commands whith time-tags. Also I
would like to explain the techniques
which are used to allow accurate
time-evaluation to provide a musical
system, which can be manipulated in
real-time
1. THE FLOW OF SOUND CHANGES.
The program of the errant syncretizer
basically consists of two mechanisms:
one provides for a shifting of sounds,
by changing parameters of the voice set
up of the synthesizer (currently a TX7).
The other part of the program records
and analyses what is being played and
generates new melodies. The main
intention of the first mechanism is to
supply the performer with an instrument,
which never needs to play a note the
same. It would be possible to obtain
that by applying a random generator,
which would randomize the voice program
of the synthesizer. However the errant
syncretizer should be a highly
controllable instrument in such way,
that the performer is able to steer the
soundchanging. This purpose can be
accomplished by letting the errant
syncretizer smoothly change the sound
and allowing the performer to intervene,
when he needs to.
Parameter Changes.
The errant syncretizer changes the voice
by sending every Â~20 msec a parameter
change to the synthesizer. The parameter
changes are calculated as follows: the
errant syncretizer chooses a beginvoice-program and a target-voiceprogram. In turn the errant syncretizer
increments or decrements a parameter and
sends it away. This effects a slow
change from the begin-voice-program to
the target-voice-program until they
finally equal each other. Then a new
target-voice-program is chosen and this
process starts again.
179
ICMC 86 Proceedings
