Musique électroacoustique latino-américaine

Manuel Rocha Iturbide, Transiciones de Fase, 1994

Durée de l'enregistrement : 10 min 26 s.
Instruments : Pour trompette, cor d'harmonie, trombone, tuba et ordinateur

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À propos de cette composition :

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Instruments: Trumpet, French Horn, Trombone, Tuba.

Electroacoustic material and Hardware: 1 Macintosh computer with Sound tools card and Sample-cell card. 1 NEXT computer with SIM-IRCAM card. 4 midi pedals. 4 microphones. (There is a new version for tape and the live electronics could be remade with Max MSP, but with the tape part only works also fine).
DSP software: SVP (IRCAM), SoundHack (Tom Erbe), Modèles de resonance controlled by Patchwork (both IRCAM), Csound (MIT) controlled by Patchwork, Sound designer (Digidesign).

"Transiciones de fase" is an interactive composition for brass quartet and computer. The goal of this composition was to make a sound research about the timbre possibilities of brass instruments (in both the acoustic and electroacoustic domain) , and to present in the piece different states of sound, as a natural element like water can have liquid, gas or ice form. The transitions between one state and the other in the piece are a metaphor of a chaos processes where we go from regularity to irregularity, from certainty to uncertainty, from stability to instability (1). The theories of Chaos have also inspired me to create the overall structure of the piece which is a sort of "fractalisation" of the ratio 3:2 which is represented by the length proportion of the sections, phrases, rhythmic motives, etc. The idea that microcosms is equivalent to macrocosms (again inspired in fractal theory) is also reflected in other aspects of the piece. The melodic and harmonic material for example were deducted from the FFT spectral analysis of Tuba and Trombone slaps, these analysis served also to make the timbral synthesis transformation in the modèles de resonance section, so Timbre = Harmony and melody. Another example are brass attacks which are granulated into smaller and smaller grains of sound. I also used the metaphor of "Phase transitions" from chaos theory (Turbulence in thermodynamics) in the macrocosms , as in the transition between different sections, masses of sound, states of rhythmic order and disorder, and in the microcosms , as in the transition in the timbre of one sound which goes from stasis to activity, such as the beating produced by playing and singing to the octave into the instrument, when the singing is slightly detuned. My aim is that all these characteristics have generated a music which evokes the complexity of different physic and biological phenomena in nature. Due to the exclusive digital transformation of brass sounds, the acoustic and the electroacoustic domain are complementary, this has helped to make the music organic. I hope also that the interaction between the instruments and the computer has enhanced this "organicity".

The electronic sounds, drawn by the instruments that play, were processed and mixed down beforehand with the computer, but there is also Digital Signal Processing in real time with the IRCAM next station. One part of the sounds processed in the studio were treated with a Phase vocoder, using the techniques of stretching and convolution (cross synthesis). The other sounds were created by analysis and re synthesis of brass instrument samples, either by using the IRCAM program modèls de resonance (2), or by using a granular synthesis control patch that I developed with Patch Work (3). In the DSP in real time I control parameters of reverb combined with filtering and harmonizer (for the first section of the piece, measures 1-28), and two spatialized delay control patches for the end of the piece (measures 116-130). For the control of the different real time parameters of the NEXT I use random algorithms within fixed graphical evolution curves. I did the same for the synthesis control parameters of the generated granular clouds. As for the triggering of sound processed at the studio, there are two direct disk long premixed sections ("modèls de resonance" in measures 29-53, and granular synthesis in measures 76-106) and some shorter. On the other hand, In the third section I use short midi sequences which control a sampler (sample cell) and which are spatialized through 8 different speakers. All events (real time, midi, direct disk) are triggered by the performers with 4 midi pedals.

"Transiciones de Fase" was premiered at IRCAM with the ensemble Court Circuit directed by Pierre Andre Valade and also played at ICMC 1995 in Banff Canada. This piece was awarded with a nomination at the Bourges electroacustic music contest en 1996 and with the 2nd prize of the Russolo contest in 1996.

1)As when boiling water is transformed into gas.

2) Here the resynthesis is made by filtering white noise and other concrete sounds such as granular synthesis.

3) I used granular synthesis derived from brass samples, and granular synthesis derived from wave forms, but this last one convolutioned (cross synthèsis) with brass sounds such as talking and whispering into the instrument or different attacks.

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