ï~~
The Technology (pitch detector driving a synthesizer) reveals to the
instrumentalist new modes of playing.
The second example is the same as above but with four TX7 modules.
The number of modules activated is controlled by the amplitude coming from the pitch dctcctor. The pedals affect sets of four timbres.
The composition of sets is stored in files specified when calling the program. Here the combination of pitch, amplitude and pedal playing
creates an improvisatory musical context. This example also shows the
response time of the software (MPU servicing, parsing, echo to the
MPU and the synthesizer): following one melodic line rnom the flute is
no problem, while the same process on keyboard chords shows delays
in the playback (arpeggiation of chords).
23.2. Example 3: Echos and Rhythms The use of Motc to build
rhythmed echos triggered by incoming pitches is shown in this example.
Rythms are read from a file (like a set of timbres in the previous
example) and indexed by switch pedals. The continuous pedal controls
global tempo.
2.3.3. Example 4: Multitrack Sequencer A version of "Auronusique",
piece number 8 of Globokar's "Laboratorium" is played. This version is
somehow different from the original specifications. The performer
depresses a pedal to enable time tagged pitch recording. When the
pedal is lifted, cyclic playback starts. If the same track is retriggered,
the new sequence is inserted. The other switch pedal increments the
track number (maximum eight tracks) and allows layers of sequences.
Each track has a different timbre. The continuous pedal controls the
playback tempo. The performer creates a context in which he improvises. All tracks are written and read on disk in realtime. Technically,
this shows realtime simultaneous MPU and disk servicing.
3. JIMMY DURANTE BOULEVARD
This piece written by Georges Bloch summarizes most features previously presented. It makes use of the CARL MPU software and the
Moxc scheduler written by Roger Dannenberg and modified at CARL
by Xavier Chabot.
3.1. Multiplication
The piece is based on the definition of a process able to multiply one
material MATl by another MAT2 based on geometric series whose
parameters arc read from a data file. The multiplication process is
notated (MATTI* MAT2). In example 6a the trumpet will enter various MAT1 sequences, while MAT2 and the development parameters
are fixed: eg. a single note, a scale, a rhythmic pattern, or a complex
sequence. In example 6b various developments are played while MAT1
and MAT2 are fixed. Development parameters are
convergence/divergence, geometric ratio, proportions of silence and
proportions of cuts into the trumpet phrase. Example 6c plays various
developments entering MAT2 from the keyboard.
3.2. Chord Analysis
A chord analysis method by Julio Estrada is used. Any chord can be
reduced and given a type number between I and 78. The type number
gives a measurement of the dissonance and the evolution of the type
number in a chord sequence gives measurement of the changes in harmonic context. Results of the analysis of any incoming chord affects
the content of the MAT2 (example 7a), activity of subvoices of the
development (example 7b) and parameter of the geometric series
(cxamplc 7c). The chord analysis software has been defined by
Georges Bloch and written by Roger Dannenberg.
33. Melodic Context Analysis
There are two simultaneous melodic context analyses: contour and concavity. They have been designed and written by Roger Dannenberg.
Both processes are enabled/disabled by the flute pedal. The contour is
defined as the integral in time with the pitch referenced to the first
pitch entered when the flute pedal is depressed. The concavity is
evaluated on a moving window of three pitches. Examples 8a and 8b
show contour and flute activity (variation of the concavity) acting on
the playback of development subvoices (activation and relative dynamics). The action of the flute is called ornamenration. See figure 2 bellow.
low activity
concave
high activity
I I
_-- t1_tt-t-1 \__----, - -_
convexe
integral: high positive still positive high negative
Figure 2 "Pitch Contour Analysis"
4. CONCLUSION
The last example is a version of the piece. Although there are many
possible versions-performers are improvising- we strongly feel the
uniqueness which makes every example belong to the same piece writ ten by a composer: this is COMPOSED IMPROVISATION. Creation of
the piece is shared between non realtime (composition) and realtime
(improvisation). Each of the above examples stimulates a particular
type of improvisation from each improviser. Thc only directive for the
performers is to know what mode the program is in. The whole piece
features complex relationships between musical context and musical
event.
REFERENCES
CttAtsor, XAVIER AND BEAUREGARD, LAwRENCE (1984). "The
flute-4X project", ICMC 84 Conference, Paris.
CthAtor, XAVIER (1985a). "User Software for Realtime Input by a
Musical Instrument", ICMC 85 Proceedings, Vancouver, B.C.
CtIABor, XAVIER (1985b). "Uses of an Instrument-Computer Synthesizer System", Music Department Seminar, UCSD.
CHADABE, JOEt. (1984). "Interactive Composing: An Overview", Com purer Music Journal, 8(I), pp. 22-27, MIT Press.
CoLucNGE, DJ (1985). "Moxie: A Language for Computer Music Per formance", ICMC 85 Proceedings, Vancouver, B.C.
DANNENBERG, ROGER (1984). "An On-line Algorithm Realtime
Accompaniment", ICMC 84 Proceedings, pp. 193-198, Paris.
DANNENUERO, ROGER AND Bioctt, JOSHUA J (1985). "Realtime
Computer Accompaniment of Keyboard Performances" ICMC 85
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GEtrr.EwAN, W.M. (1985). "Using the Harmony Operating System",
ERB-996 (24685), National Research Council of Canada.
GLOBOKAR, VENKO (1975). "Individuum Collectivum", unpublished,
Paris.
GLOBOKAR, VtNKO (1986). "Laboratorium", unpublished, Paris.
Loy, D. GARET1t AND WRIctrr, RUSTY (1985a). "An Operating
Environment for a Realtime Performance Processing System" ICMC 85
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LoY, GAREtrit (1985b). "Player - Extension to the C programming
language for Parallel Processing and Music Synthesis Control", unpub lished, Center for Music Experiment, University of California.
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from Musical Imperatives" ICMC 86 Proceedings, The Hague, Holland.
ROADS, CURTIs (1985). "Improvisation with George Lewis", in Composers and the Computer, Kaufman.
MAntsws, M. V., AND MOORE, F. R. (1970). "GROOVE-A Program to Compose, Store, and Edit Functions of Time", Communicasiou
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