The sound material used in E pur si muove… resulted from a series of experiments with Symbolic Sound’s Kyma / Capybara 320 sound computation system. I tried to implement analogue patching techniques based on my experience in the Institute of Sonology’s voltage controlled studio.
When I attended Jaap Vink’s classes during the Sonology one-year course in 1981, one of the synthesis models he showed consisted of a feedback setup with ring-modulators, filters and delay lines. In this model, a sinewave oscillator is connected to a ring-modulator; the output is fed through a compressor, a reverberator, a filter and a delay line (a tape recorder) into the second input of the ring-modulator. With some amplification in the feedback loop it is possible to gradually build up a complex sound which gradually changes its timbre over time.
A more complex setup involves four oscillators, four ring-modulators and four delay lines, providing a wider range of sounds and quadraphonic output. This setup was now digitally implemented in Kyma and the results are used in E pur si muove….
Kyma patch example 
Kyma virtual control surface
In the final version of the patch, the following parameters are defined:
| Osc. Levels: | Output level of the 4 oscillators. |
| Osc. Freq's: | Frequency of the 4 oscillators. |
| Second sine Freq: | Frequency of a mixed-in second sine wave. |
| Second sine Level: | Output level of the mixed-in second sine wave. |
| Noise Freq: | Frequency of a filter that controls the band-pass of a mixed-in noise generator. |
| Noise Level: | Output level of the mixed-in noise generator. |
| A250Hz, A500Hz, A1000Hz, A2000Hz, A4000Hz, A8000Hz, A16000Hz | Output levels of a group of band-pass filters inside the feedback loop. |
| Mod Freq: | Average frequency of a slow random-frequenc -modulation of the four main oscillators. |
| Modulation Depth: | Depth of the slow random-frequency modulation of the four main oscillators. |
| Spreiding: | Distance in frequency between the four main oscillators (a setting of 0 = equal frequency). |
| Porta: | Transition time of the parameters to the settings of a new preset. |
| Delay: | Delay time of the four delay lines in the feedback loop. |
Another technique I wanted to implement in Kyma was ‘tendency masking’ as I used it in my composition Geoglyphs. However, instead of designing a complex series of different masks, I decided to base the mask shapes on slow triangle-shaped control signals, as shown in the following picture:
The staircase-like figure results from sampling values within the mask’s range.
The model implemented in Kyma uses two of such masks: one to control the limits of 4 random sources for the frequency of 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’s limits are visualised 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.
Disk recordings of this patch were also used as a source for further sound transformations, which appear in subsequent sections of E pur si move….
year: 2001
duration: 15:05
tracks: 4
Available on the CD Kees Tazelaar: Electronic Compositions (CV NEAR 13)