VOSIM + FILTERS

Patches were created in BEA5 exploring the combination of VOSIM and filter modules. Sine wave oscillators were also used as modulation sources for the patch.

The parameters provided by the VOSIM module give a logical and wide control over the spectral characteristics of a sound. More specifically, the VOSIM oscillator is a tone burst generator which provides parameters for number of pulses, the decay of their amplitudes and the frequency at which to trigger this set of pulses. This combination facilitates the production and manipulation of formants/vowel sounds
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More information about the VOSIM synthesis approach can be found here: http://www.atiam.ircam.fr/wp-content/uploads/2011/12/AES_JAES_1978_Kaegi_VOSIM.pdf

In addition to this, the use of filters and the modulation of their cutoffs helped generate more dynamic timbres. This was particularly effective when creating complex phase relationships between the modulation signals for the inputs of the oscillator and filter.

When the modulation signals are close to each other in frequency, longer subtle phase shifting is created. However, when the frequencies are more distant the beating patterns become faster. In addition to this, the harmonicity of the relationship between the two signals can be used to control the complexity of these patterns, with more dissonant ratios/intervals producing more less repetitive/longer patters that are harder to follow.

AUDIO: https://www.dropbox.com/s/dbs7i6a9f5fxh6d/15thfebBEA5chop.aif?dl=0

Whilst exploring the module, I found myself drawn towards triggering the module at lower speeds to create and articulate trails of pulses. This inspired further exploration of this oscillator using SuperCollider to generate pulses that were used to excite filters and resonators. The use of simulated resonators such as the MembraneCircle and Streson UGens create richer results with subtle evolving details due to the accumulation and decay of resonances.

In addition to this, when the filters are placed one after another, the similarity/distance between resonant frequencies of the two filters produces interesting beating patterns. Although, when the resonances of the oscillator and two filters coincide they amplitude of the sound can increase dramatically due to the nature of resonance and the feedback systems used to emulate it. This was particularly noticeable when using the mouse as continuous modulation source for the resonant frequency of the filters and gain compensation may have to be added later if this becomes too dynamic and difficult to control.

In addition to this, the amplitude of the input signal was also used as a modulation source for the tension of the membrane. This accentuates the natural pitch changes that occur when exciting an acoustic membrane. In this way, these simulations allow for the amplification and attenuation of sensitivity towards certain aspects and reactions of the instrument.

CODE: https://www.dropbox.com/s/d7m7mjyvfet7001/17thfebVosimReson.scd?dl=0

AUDIO: https://www.dropbox.com/s/upm0n3p0z9xl0zm/17thfebVosimBraneCHOP.aif?dl=0

https://www.dropbox.com/s/vj4kfr7k66wgr3h/17thfebVosimBraneKarplus.aiff?dl=0

https://www.dropbox.com/s/70yr323pg0gc123/17thfebVosimBraneKarplusXY.aiff?dl=0

Similarly, these experiments also incorporate ideas from previous explorations combining granular oscillators and convolution. This code uses the amplitude of the granulator to crossfade between two convolution synths with different impulse responses. This gives the sound a sense of movement, reducing the flatness of the sound caused by precise repetition of the impulse response.

CODE: https://www.dropbox.com/s/beclvekuwqz5qit/grain2conv.scd?dl=0

AUDIO: https://www.dropbox.com/s/9o0oz62cle6kca5/9thfebGrainsConvReson.aif?dl=0

After listening back to the results of these experiments it occurred to me that the VOSIM could be used as an envelope generator, allowing choices to be made about the spectral content of the pulses.
Firstly, pink noise was used as a source signal and produced a  thicker, punchier sound due to wider spectrum of the excitation signal.

AUDIO: https://www.dropbox.com/s/xy06dwj9jv66mmi/18thfebVosimPinkNoise.aiff?dl=0

The laptop's microphone was also used as a source signal. This became particularly interesting when used in combination with the amplitude follower to manipulate the speed of the VOSIM oscillator. This allows articulation of the pulse streams using the acoustic sound, with faster speeds being produced as louder sounds are made. In this way, the resultant structure/form is derived from the material as the pulse trails are influenced by their content. In addition to this, the feedback between the microphone and speakers increased the complexity of this relationship, resulting in more engaging interactions in which the balance and thresholds of resonance can be explored.

AUDIO: https://www.dropbox.com/s/ale48hdpyryuh2b/18thfebVosimSoundIn.aiff?dl=0

These concepts could also be expanded by incorporating pitch/centroid tracking to control the resonant frequency of the filter. However, the correct scaling between the two still needs to be found.

Patchbay, Feedback and Transducers

Several experiments were carried out exploring various combinations of transducers, acoustic objects and DSP software. The patchbay circuit was placed in a temporary enclosure and used to control the routing of signals between these elements. Banana jacks were connected to several of the inputs and outputs of the patchbay facilitating the navigation of the interface due to their larger size and circular layout.

The placement of various objects between the input and output transducers allows the 

use the objects to filter the sound acoustically. By adjusting the positions of the transducers on the objects, different resonant modes can be excited. In this way, the transducer resembles a stethoscope or microscope, amplifying and revealing, allowing explorative listening to the internal structure and material qualities of the object.

This process becomes particularly intriguing when exploring combinations and couplings between multiple objects, producing a wide range of rattling and buzzing sounds. More specifically, bike spokes were used to create temporary structure/sculptures which could be explored by manipulating the distances, pressures and surface area between the transducers and objects. In addition to this, the constant vibration of these structures in combination with the multitude of parameters and forces involved leads to a certain unpredictability and  constant evolution in the sound.

More specifically, these experiments aimed to use the feedback tones created between transducers as raw sound material which can be dissected, processed and rearranged using SuperCollider. In addition to this, techniques for destabilising the dominant resonant tones were also explored, softening the threshold for explosion/entrainment/sympathetic resonance and allowing the system to be controlled more easily.

A combination of delays and reverb were used to reduce the speed of the feedback process. This results in a more controllable system, providing the performer more time to react to changes in the sound without losing the sensitivity provided by the acoustic interactions. Furthermore, this allows for a more detailed and contemplative listening to this iterative filtering process, as the initial sound slowly takes on the qualities of the object, creating a complex intermingling of objects and identities.

Filters were added to the input signals, allowing the performer to selectively excite and explore the various different resonances of acoustic objects. In addition to this, the amplitude of the input signal was mapped as a modulation source for the filter's cutoff and resonance. This creates more complex interactions between the electronic and acoustic sounds, destabilising the dominant feedback tones as the resonant peak is always moving. This is particularly interesting as it produces short trails of feedback as the amplitude of a sound rises and decays.

The extreme sensitivity of the system to volume changes and the precision required to bring feedback tones in slowly can be particularly problematic and usually requires the performer to make constant adjustments to the volume. Possible solutions to this problem could include the use of a volume pedal with some mapping to soften the response curve. Compression could also be used to reduce the dynamic range of the audio signal.

The placement of additional loudspeakers on the same table as the amplified objects provided a richer and more engaging experience. This is partly due to the wider frequency range of these speakers but also because interactions with the air surrounding the speakers start to influence the sound. Every subtle movement becomes amplified and significantly influences the sound. 

In this way, the amplification allows the exploration of sound as a physical phenomena, as vibrations in the surrounding space. This experience also has similarities to early explorations of acoustic instruments. In particular, the process of becoming aware of the subtle movements of the body that produce nuanced timbral fluctuations and learning to control and shape them.