Javier Alejandro Garavaglia
Gegensaetze
(gegenseitig) for alto flute, 4-Track Tape and live-electronics (1994)
Genre: Instrument
+ Tape + Interactive
Duration:
33 Min.
PARTS OF THE
FOLLOWING TEXT APPEARED ON THE PROCEEDINGS BOOK OF THE 2nd
BRAZILIAN SYMPOSIUM ON COMPUTER MUSIC (SCBII) IN AUGUST 1995.
PAPER READ
DURING THE CONFERENCE HELD IN CANELA (BRAZIL)
THE
NECESSITY OF COMPOSING WITH LIVE-ELECTRONICS
A short account of the piece "Gegensaetze (gegenseitig)" and
of the
hardware (AUDIACSYSTEM) used to produce the real-time
processes on it.
Javier Alejandro Garavaglia
Hendrik-Wittestr.
11
45128- Essen.
Deutschland.
(Germany)
Tel:
(0049-201-229831)
E-Mail Address:
gara@folkwang.uni-essen.de
ICEM- Folkwang-HochsChule Essen
Klemesborn 39 /
45239- ESSEN. Germany
ABSTRACT
The
aim of this paper is to present my piece Gegensaetze [gegenseitig]
(in English: Contraries [reciprocally]) for alto flute, 4 Channel-tape and live
electronics (1994)- making an account of how and why the work was conceived.
The hardware-and-the-software environments which are responsible for the
real-time processes (AUDIACSYSTEM, a project carried on by the ICEM (Institut
for Computer music and electronic Media) at the Folkwang Hochschule-Essen and
"CONTRARIES
"
Gegensaetze
(gegenseitig) was the result of an idea that I have had for a
long time: to compose a piece in which contraries should be shown not only
against each other (in a negative way), but also that they could be able to
build some kind of unity by creating something completely new, constructive and
positive.
My
first challenge was how to put this into music without using a text about the
subject. At the beginning I simply wanted to make a contrast between a normal
instrument and a pre-recorded tape, but it didn't seem like being the solution
to the problem because it could actually show only the contraries themselves
but not the reciprocal action of both elements. The instrument should make with
the electronic something really new and this should happen in real time and not
with recorded material. That was the reason why I first began to work on the
tape itself, making sounds with two Yamaha synthesizers (TX 802 - TG77) that
shouldn’t have any relation with normal instruments. I composed then a
previous piece for stereo-tape alone, from which I took the materials for the
work’s definitive version.
Once
the tape materials were selected, I knew already that the instrument should
have to be a very soft one, and the election was that of an alto flute. How
should then the "reciprocal action " look like? I was now pretty sure
that it should be performed with live-electronics. This decision conduced me to
the next problem: what type of live-electronics did I really want and much
further, which kind of system should I use?. There are basically two ways of
working with live-electronics: on one side, those whose aim is to create a new
conception of how the live instruments could be projected into a particular
space or room, normally using only echoes and delay lines; on the other side,
the more complicated ones, in which the sound will be actually processed in
real-time (through FM, AM, filters, envelope generators, envelope-followers,
transpositions, etc) up to the point in which the instrument itself could be no
longer recognizable.
At
the ICEM of the Folkwang Hochschule in Essen (Germany), there was no ISPW, but
a completely different project, which has been carried on since eight years at ICEM by a group of German composers and engineers. This project is the
AUDIACSYSTEM, about which I shall speak later in this paper.
Once
I had already got the three Instrumental groups (alto flute, 4-channel tape and
the 4-channel live-electronics), I wanted to prosecute composing each parameter
(from the micro-up to the macro-structures) with the same concepts of
THESIS-ANTITHESIS working together to create something new, so that at any
point of the piece the main idea could be shown. For this purpose, I've chosen
two principles opposite to each other:
- "single-principle"
- "totality-principle".
Both
principles are the main generators of every event throughout the
work and are mainly represented everywhere in the piece by two objects: a
"glissando-object" representing the "totality-principle"
and a "single-note-object", representing the
"single-principle".
For
the whole structure of the work a numerical-row was chosen, whose first four
components were explicitly selected by myself, but from the 5th component on,
they should always be the addition of the last three numbers (that means that
the next figure in the row will be constituted with the reciprocal action of
the former three). It comes as result a bigger new value standing as a contrary
to the first, for example, the row begins with (1 1 3 5), which are the numbers
that I arbitrary selected; the next value will be 9 (1+3+5), the next 17
(9+5+3) and so on. Each single element contributes to make a partial new
totality. This row plays an extremely important role in the composition
of the pitches, rhythms, metronomic values, form, and
the stage-production, as well.
The
form of the piece consists of 5 sections, each one showing the principles already
mentioned:
1 -
Solo alto flute ("single-principle")
2 -
Alto flute + Tape (as opposites)
3 -
Only Tape ("single-principle")
4 -
Alto flute + Tape + live-electronics ("totality-principle"-
reciprocally action of all three)
5 -
Only live-electronics ("single-principle" as result of the
reciprocally action of all three)
Rrhythms have been also composed with the numerical row: there is a unit value (the sixteenth or semiquaver), which will be multiplied and divided with the numbers 1,
3, 5, 9, in all possible combinations within these 4 numbers (for example,
ratio 9:5 means that 9 equal durations should be instead of 5 sixteenths;
ratio1:3 results in a dotted eight, etc.).
The
stage-production works also with contraries: the stage is only illuminated when the flautist plays (parts 1, 2, 4 and 5). In part
3, where only the 4-channel-tape is present, the whole stage and the whole hall
(if possible) should be dark.
The
materials for the pitches were derived from a chromatic scale beginning with
the pitch G3 (the deepest note for the alto flute in G), representing a whole
or totality object, a meta-symbol of the "glissando-object ".
This object plays one of the most important roles throughout all parameters in
the piece, not only for the flute-part, but also and mainly for the tape and
the live-electronics. The process of generating the whole pitches for the flute
part are produced by an algorithm that eliminates some notes in such a way that
at the end, there's only one pitch left. The result is a process going from the
whole (all 12 tones) up to ONE SINGLE element, generating a tension between the
two main principles mentioned above. The pitches which were eliminated, will be
used later in part 4, in the form of 3 improvisations, in which only the
rhythms are totally free. These improvisations make a counterpoint to the
live-electronics and even modulate them, as it happens in the third
one.
The
whole 4-channel-tape part was produced and composed using different programmes,
procedures and methods, i.e. CommonMusic, transpositions and filters (mostly
with Sound Designer II), echoes and even with the AUDIACsystem itself. The
about twenty minutes long 4-channel tape makes at its beginning a counterpoint
to the alto flute, then develops thereafter alone and finally, it fades out very
slowly as the live-electronics start.
THE AUDIACSYSTEM
The
AUDIACsystem iss a project developed at the Folkwang-Hochschule in Essen
(Germany) by the ICEM (Institut for Computer music and Electronic Media) and
the Micro-Control GmbH & Co KG. The people involved in its whole design
are: Dr. Helmut Zander, Dipl. Ing. Gerhard Kümmel, Prof. Dirk Reith and
the German composers Markus Lepper and Thomas Neuhaus. The whole began in 1987
and attaches not only the hardware architecture, whose specially designed Audio
Processor Unit has got the power of 2,5 Pentiums (1st generation) -
naturally regarding only the audio processing capacities- but also the software
itself, which was exclusively created for this particular environment.
The
hardware configuration employed in my piece should be contemplated today as an
already finished stage of its own development, because almost the whole is
going to be actualized, replacing the current design with a new one, which
shall result in a chain of Pentiums or most probable P6s, acquiring a RISC-
processor configuration and making the whole a bit smaller than today's one
cubic meter, possibly making it also compatible with a Power-PC.
HARDWARE
CONFIGURATION
The
hardware configuration of the AUDIACSYSTEM is shown on the following schematic
representation:
The
hardware architecture of the AUDIAC has been conceived with the principle of
the specialized subsystems. It has not only been made to generate
organized forms for the musical production, but also incorporates the
generation and working up of sounds in real-time. The whole implies a huge
measure of different demands in relation of its computing potential, which can
only be solved with the above mentioned subsystems and their communication
capacities.
The
whole system could be described as the cooperation of a "von-Neumann"
unit on the one side and a Signal-processing unit on
the other. The former perceives configurations (devices), control and driving
functions, which steer the processes of generating and working up of sounds
from the latter. The communication is guaranteed with the help of the Multibus
II. The "von-Neumann" part
consists of a Manager (APM) and one or more control units, the APCs. Both do
communicate via SCSI.
The
APM (Audio Processor Manager) is a 486 Computer with a 66 Mhz clock-rate, where the software
specially designed for the AUDIAC is implemented. This software is the language
APOS which means Audio Processing Operating System and which was specially
created by the German composer Markus Lepper for this purpose. APOS pursues
three goals, which are:
(1) a monolithic system architecture, in terms that
every hard-and-software levels could be described with the same language, from
an individual bit of the hardware up to very complicated abstract compositional
models;
(2) an enlargeable anthropomorphic surface, in the sense that each
composer can use not only algorithms that are already defined but also can
implement his own language for a particular use as well;
(3)
an abstraction from the technical necessities, meaning that composing should be
allowed on a symbolic level, without caring about technical details.
APOS
is an object-orientated language that works with two levels of interpreter: an
outer interpreter, which receives the information in ASCII code, and an inner
interpreter, which reads a row of object-references, which are references about
objects that already exist and could be recognized as such. The software runs
in protected-mode because of memory management reasons, and makes possible that
some kind of tasks - which are necessary for the actual configuration of the
system - can be perceived.
Regarding
the APCs (Audio Processor Controller), the system can afford from only one up
to four units. These are all "186" computers which, due to the ATOS kernel (a
real-time operating system kernel specially developed for musical applications)
have got many functions at their disposal, which are needed for the
multitasking operations. The ATOS configurations are created on the APM in APOS
and will be later called by the APC, generating or working up sounds. The APC
and the Signal processor run asynchronously. The heart of the APC is the APU
(Audio Processor Unit), the real Audio processor. Beside it, there are a number
of auxiliary units, such as the AOC ( a unit capable of transferring data and
time code between the APUs, also from one to other two simultaneously, and
which could be programmed separately; the CIN (a low control interface with a
16 times multiplex A-D converter, through which up to 16 control voltage units
could be brought in); the AIF (the A-D and D-A converters). The APU consists of
one Memory Unit (MAU=Memory Address Unit) and an arithmetic unit (AAU, a
multiplier). It is possible to put up to 4 APU plus one AOC together, connected
through a z-bus. The data could be read and written on the Multibus II. The two
memories of the APU (XMY and YMY) can be addressed alone or parallel. The
in-and-out sample ports work with the Fifo principle and connect the APU with
the out world through the A-D and D-A converters. The interface has 2 inputs
and 4 outputs, which could be enlarged up to 32 and 64 respectively. The
computing processes run parallel, that means that it could make up to two
additions (or subtractions), one multiplication, twice read and write from and
to the D-RAM (or four times from the S-RAM) at once. The flexible handling of
the signal processing unit is guaranteed due to its totally free way of being
programmed. The synthesis or working up of sounds result from micro-programmes
specially developed for this APU.
The
Parameter-Functions-Generator (PFG), which is a computing unit in itself works
within the APU. It is coupled on one side to the APU and can (due to its
complexity) be seen as an independent unit. Its multiple possibilities of
application could be resumed in the providing of control instruments for the
manipulation of sound: envelopes, spectral control, sound intensity, etc. For
each parameter to be controlled, there could be placed pro time-unit one
"value-pair" plus a bit-control. Each sample of every four could take
a new PFG value. There are altogether 128 PFG free for each APU. The PFG has
basically two operating modes: one, in which a "value-pair" INC/FIN
makes a linear interpolation, building an envelope which makes a continuous
alteration of the y values through the time axis; the other, which interprets a
"value-pair" y-dt , where y takes one value
and dt represents the duration of it, building discrete
values. The control-bits allow a flexible and interactive influence to the
corresponding value rows, for example: back to the first value, mode switch,
segment switch-interrupt and hold function (fermata). Interrupts are possible
in the first operating mode over each FIN value; in the second mode, at the
moment of any new y-value. Through the use or the interrupt features, new
support values can be called, resulting in more support values for only one
parameter function.
Microcodes
The
biggest time unit to take account of is that of the Sample-rate. The time
between two samples will be called "MINICYCLE". There are multiple
"cycle calculations" within such a "MINICYCLE" which are
coordinated to different process channels (PROK). One cycle calculation can be
divided into a given number of microcycles, which correspond to that of the
machine rate, which is normally set at 10 MHz. All calculations necessary for
the generation of a sample must occur within a single "MINICYCLE".
The cycle will be finished with a reset signal, which guides to the next step,
that is the D-A conversion. With a sample-rate of 48 kHz., the duration of a
"MINICYCLE" comes up to around 20 micro-seconds.
WORKING WITH THE AUDIAC system
The
way in which the input data can be programmed, may be defined in two different
forms: on the one hand, it could be done algorithmically; on the other hand however,
a specially pre-composed material could be later imported to the system. Both
possibilities don't exclude each other, but could be mixed throughout a
composition, which is actually the case of this piece. The resulting Score can be
defined anew in two different ways: statically, creating discrete values
for the structure, or dynamically, in which the begin and end of each
event is particularly significant, because any kind of process can be
programmed between both extremes (for example, transpositions, dynamical
filters, etc). This data will be then translated, resulting in a row of orders
to be interpreted and fulfilled.
Coming
back to the piece, the ca. 13 minutes long live-electronics part is divided
into three different groups: "LA", "LB", "LC",
"L" meaning in this case "live".
For the programming in APOS, I had got the invaluable help of Markus Lepper,
who I've already mentioned as the creator of this language.
Regarding
the first part, "LA"- with a tempo of quarter equal 50 and measure
3/4 - the AUDIAC system records three different types of single events played by
the alto flute, namely: breath-out-noise, one multiphonic and a row of slap
tones played separately. They will be played back with intervals of 9, 5 and 3
quarters (proportions taken from the numerical row, which I spoke about in the
first part of this paper), rotating from one channel to the other anticlockwise, in opposition to the tape's channel
distribution: 1. front-left, 2. front-right, 3.
right-rear, 4. left-rear.
The
recording of the different sounds is made through an object defined in APOS as
"RECORDER", which works in such a way as a normal recorder. It has a
begin- and an end-buffer-time, an amplitude value, etc. The samples recorded
will be played by another object, the "Player" which also has a
begin- and an end-buffer-time, an amplitude, an input to vary its frequency
("FINC" transposing the sample) and an input to loop the sample from
a given buffer-time-point. There are four players, each one corresponding to
each one of the four channels. Each recorded sound becomes a different memory
address, so that it could be called at any time. For the time allocation of
these events, the computer was asked to find the best possible distribution
through all four channels between space and time, in order to force the events
to meet quite often at one same channel. When this actually happens, one event
will multiply the other, modulating each other (Amplitude Modulation). When all
events (once breath-out-noise, once a multiphonic, and five times different
slap-tones) have been played and recorded, the computer begins to transpose
the information of 3 of the 4 players with different ratios (which are taken
from the numerical-row). This transposition, made through the input
"FINC" of each "Player", takes place dynamically, that
means that within its time limits given in the score, the frequency will be
varied every fourth sample, making "glissando-structures".
For
part "LB", there are two moments to be recorded, both 12 seconds
long. This part makes a formal "crossfade" with "LA", and
is all about transpositions on all 4 channels of both recorded materials. These
transpositions, however, are not dynamical, but discrete. The first of the two
recorded materials of "LB", must be further stored, because it will
be used in the next part "LC".
The
score for "LB" is programmed half algorithmically and half
pre-composed, as the following APOS example demonstrates:
new plstarts
"pls2" 200
* open pls-kanal 0
*;
ANZAHL ABSTAND
*; EINSAETZE
* put pls2 1 * 17
* put pls2 3 * 9
* put pls2 5 * 5
* put pls2 9 * 3
* put pls2 17 * 1
*
* apl pls2 110 to 150
[ if [[_1 mod 21] ?eq (110 mod 21)] ['@ .p0 _0 ok] ]
* apl pls2 111 to 150
[ if [[_1 mod 19] ?eq (111 mod 19)] ['@ .p1 _0 ok] ]
* apl pls2 112 to 150
[ if [[_1 mod 15] ?eq (112 mod 15)] ['@ .p2 _0 ok] ]
* apl pls2
113 to 150 [ if [[_1 mod 9] ?eq (113 mod 9)] ['@ .p3 _0 ok] ]
All
these lines describe every starting point of every of the four players. The
last four lines use an explicit indication (pre-composed) of how the structure
should finish; on the other side, the "put" lines use an automatic
way of creating the starting points with an special syntax implemented for this
purpose. This syntax will be implemented with the following APOS source text:
new latch
"pls-kanal"
* new latch "pls-Position"
*
*; 4 new methods are
going to be defined for this purpose (dm)
*
* dm [ put (any plstarts) @ (any integer)
.p (any integer)
*>
(any integer) * (any integer) ]
*> [ apl 0 to [pred _6]
*> ['@
pls-Kanal ['['_5 + __0] MOD 4] ;
*>
@ pls-Position [' _3 + ['_8 * ['SUCC __0]]] ;
*>
~do _0_1 ]]
*;
* dm [ ~do put (any plstarts) ]
*> [ @ .p [pls-kanal] [@ _2
[pls-position]] OK ]
*;
*
* dm [ open pls-kanal (any integer) ]
*> [ @ _1_2 ; @ pls-position
(INTEGER 0) ]
*;
* dm [ put (any plstarts) (any integer) *
(any integer) ]
*> [ _0_1 @ [pls-position] .p
[[SUCC[pls-kanal]]MOD 4] _r2 ]
The
evaluation of both texts results in a abstract-time-structure which could be
edited either manually or automatically. In this latter case, it could be
submitted to different processes of automatic transformation and
interpretation, being the actual generation of sound only one of the multiple
possible steps of such a chain.
The
last part, "LC", begins with three eight-measure long statements of
the alto-flute, which will be recorded and played by each speaker with an
interval of 3, 5 and 1 quarters (the corresponding tempo is now quarter=90, the
measure remains 3/4), making a canon that wanders all over the 4 speakers.
Between each of these eight-measure statements, the alto flute plays three
improvisations, whose durations are respectively of 9, 17 and 31 seconds. The
third one modulates the frequency of the recorded signal of all three parts of
the canon, and the result of this modulation will be anew recorded and again
modulated from the alto flute. From this point on, the flute doesn't play any
more, and the resulting modulation will be amplitude modulated - with the first
element of "LB"- than it will be transposed dynamically. The
transpositions will be gradually filtered with a notch filter,
whose frequency is around the pitch f#5 and whose bandwidth will be dynamically
narrowed up to this pitch. At the end there's only a filtered f#5 left, making
an opposition to the first note of the piece, which was g3 (last and first note
respectively of the chromatic row used as pitch-material).
Gegensaetze
(gegenseitig) was the first piece of music using the
AUDIACsystem in a real-time live performance. Up to its premiere, the system
had only been used to steer another type of events (all within electronic
music production), but there were no pieces with live instruments composed
especially for and with the system.
Although the general conception of the work can be interpreted from several points of views, my intention was to show the "Thesis-Antithesis" concept at the light of human, social and naturally also political relationships. I think that nowadays, a time in which Neo-nazi ideas and deeds wide out again (mostly in Europe and in the USA, but not only), the concept of a reciprocal action of opposite elements may be considered as the contrary to intolerance, racism and discrimination. That doesn't mean neither that my piece has got a secret program nor that it is a political work (which is mostly the case of Luigi Nono's music, to take only one example), but it may be able to recall these type of implications.
The piece was first performed on June18, 1994
in the city of Dortmund (Germany) by the German flautist Christianne Schulz.
--------------------------------------------------------
June
1995 – revised 2006-07-28