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E PUR SI MUOVE...
2001 15:04 4
       
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The sound material for "E pur si muove..." is the result of a series of exercises I did in order to get an understanding of the Kyma / Capybara 320 sound computation system from Symbolic Sound. To give my experiments a framework, I decided not to loose myself in the incredible amount of examples that comes with the Kyma software, but to try to implement analog patching techniques that I am familiar with from my experience in the Voltage Controlled Studio of the Institute of Sonology.

When following the classes of Jaap Vink during the Sonology course of 1981, one of the most impressive techniques he showed the students consisted of a feedback setup with ringmodulators, filters and delay lines, that was his own development.
Instead of the usual two signals, now only one sine oscillator is connected to the ringmodulator. The output is fed over a compressor, a reverberator, a filter and a delay line (tape recorder) into the second input of the ringmodulator. With some amplification in the feedback loop, the small amount of tape hiss and some leak of the sine to the output of the modulator are enough to gradually build up complex sounds that keep changing their timbre slowly over time.

A more complex setup involves four oscillators, four ringmodulators and four delay lines, providing a wider range of sounds and quadraphonic output. This setup is now digitally implemented in Kyma and the results are used in this piece. To get the system working, the tape hiss and the leaking of the oscillator had to be simulated too.

Kyma patch example Kyma virtual control surface

In the final version of the patch, the following parameters are defined:
Osc. Levels: Output of the 4 oscillators.
Osc. Freq's: Frequency of the 4 oscillators.
Second sine Freq: Frequency of the mixed-in second sinewave.
Second sine Level: Output of the mixed-in second sinewave.
Noise Freq: Frequency of a filter that controls the band-pass of the mixed-in noise generator.
Noise Level: Output of the mixed-in noise generator.
A250Hz, A500Hz, A1000Hz, A2000Hz, A4000Hz, A8000Hz, A16000Hz Output levels of a series of band-pass filters within the feedback loop.
Mod Freq: Average frequency of slow random frequency-modulation on the four main oscillators.
Modulation Depth: Depth of the slow random frequency-modulation on the four main oscillators.
Spreiding: Distance in frequency between the four main oscillators (a setting of 0 = equal frequency).
Porta: Transition time of the free parameters to the settings of a new preset.
Delay: Delay time of the four delay lines in the feedback loop.

 

Another voltage control technique that I wanted to implement in Kyma was the idea of 'tendency masking' as I used it in my composition "Geoglyphs". Only now, instead of designing a complex series of different mask shapes, I decided to leave the generation of the masks to slow triangle-shaped control-signals as is shown in the following picture:
 
tendency mask based on triangular shapes  

The staircase figure is the result of sampling values within the mask-range.

The model implemented in Kyma uses two of such masks: one to control the limits of 4 random sources for 4 oscillators, and one for another set of 4 random sources to control the oscillators that modulate the frequencies of the first set. The mask-limits are visualized in the virtual control surface as red horizontal lines moving up and down. From left to right they represent: Lower limit of the carrier-frequencies, Upper limit of the carrier-frequencies, Lower limit of the modulator-frequencies, Upper limit of the modulator-frequencies.
 
Kyma virtual control surface  
Disk-recordings of the output of this patch also were used as a source for further transformations presented in the piece as it develops.

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