LUIGI MARINO

musician

Interaction 2 (2018)

For any source and 6-relation-interactive system


Interaction 2 is a work that uses the computer's analytical capabilities to surround the performer's gestures with an immersive synthetic landscape. This landscape requires no intervention other than the sounds produced by the performer for its whole development. These sounds are converted into a wide variety of data which are then recombined to generate all the aspects of the computer's response. The computer's output is entirely synthetic and there is no use of sampling or timeline sequencing.

The work is divided in two distinct sections. The first one is responsive to the sounds produced in that exact instant, but its response is tangential: the spectrum analyzed is spread over a larger timespan, and often the computer recombines data coming from sounds produced at different time. The second section uses all the data accumulated during the first section to generate an independent landscape with close formal ties to the sounds produced by the performer in the first section. The time intervals of the percussive synthetic sounds are the reverse of the intervals of the onsets of the sounds analyzed in the first section; the spectral content of the synthetic sounds is a result of data recombination of the spectra of the analyzed sounds; the overall duration is the smaller part of the golden ratio (0.382) of the overall duration of the first section.

In this version I'm driving the system with a crackle box. The crackle box is a circuit designed by Michel Waisvisz in 1974. The original circuit consists of an operational amplifier (LM709) whose connections are brought on the control surface, and left open. The user, touching them, closes the circuit using the body as conductor. The sounds produced are related to the resistance of the body, and the amount of pressure applied on the connectors. The classic crackle box used the integrated circuit LM709. Unfortunately the LM709 is not that easy to find, so instead I used the schematics of John Richards's bed of nails, which uses a far more common IC, the LM356. The op amp inside the LM356 is more stable and less prone to surprises, but in the bad of nails this is compensated using both the op amps on the IC, basically creating two crackle boxes feeding back into each other. On top of that there is a white noise generator made amplifying the background noise of a small 10 Ohm resistance connecting pin 2 and 3. The connection is done manually, pushing with the finger the resistor on the pad, so it's possible to control the white noise in a fairly performative way.


More about the relations

Relation 1 - This relation is tangential and uses spectral techniques. Every 6 seconds an FFT frame is taken, and some of the frequency/amp pair of the most prominent partials are assigned to banks of resonant filters. The banks are six and crossfade into each other providing a slow and dense morphing. The selection of the frequency/amp pairs follows a user-defined pattern based on one important parameter: how much the spectral content of the filters bank have to resemble the input. When a spectrum more resembling the input is desired the program uses the most prominent partials; when a spectrum more tangential is desired, the progrm discards the laudest and selects the quietest ones. The overal amp is always normalized but it preserves the amp ratio of the FFT partials. This relation requires a continuous input, so when there is no sound to be analyzed it uses a silent loop created with the last part of the input sound.

Relation 2 - This relation is more direct in terms of rhythm, and independent regarding the spectral content. The intervention of the synth are a replica of the onsets of the input with a 10 sec delay. The synth has an algorithmic behaviour because the timber changes with a preset morphing driven by transitions that are random in time.

Relation 3 - This relation

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