Ricercar (for electric violin and stochastic step-sequencer) 2016

Ricercar was created as a way to create evolving polyphonic textures in a ‘solo’ violin piece. It uses a midi foot controller (currently a Behringer FCB1010) to control an electric violin into a piece of software created specifically for this piece.

setup.JPG

Testing at home before the first performance
foot controller, violin and laptop visible in the
chaos of pre-event preparations

The work is essentially fugal, relying on live sampling to create the layers around the instrumental part and uses a 3 layered sequencer to achieve this. Each layer contains a series of buffers which can be recorded into. The top layer has seven 5 second samples, the middle has 5×17 and the lower has 3×71 second samples. These all prime durations so when left to their own devices they will take a long time to ever repeat in precisely the same configuration. Using a foot controller to trigger when to start recording and which buffer to record to or overwrite, thus it is possible to gradually build up a four part texture using the three sampler ‘lines’ and the live violin.

loops.png

Overlapping prime blocks 5,17 and 71

In itself this is passable, but could be rather recursive and very quickly get repetitive unless loops are overwritten regularly, which in itself could become an oft-repeated task. This has been overcome in 2 ways. The first is that each time a sample is due to be played there is a 50% chance that it will not be in which case the sequencer just moves on and waits until the next step is ready and then re-rolls its virtual dice. When scaled up over each of the 3 layers of fast, medium and slow samples this means that there will probably always be something playing (depending on how many samples have had audio recorded into them!) but the thickness of the texture will vary.  The second way that diversity is added is by changing the playback speed of each sample. As a sample is triggered the sequencer takes a decision as to what pitch/speed to play the audio. This varies over four octaves (two up and two down) and results in a shift in playback of between quarter speed and four times as fast. The speed changes are in discrete even tempered steps and thus a broader sense of harmony and polyphonic/contrapuntal line can be achieved.pitch.JPG

In addition to this audio focused processing there are 2 global controls. The first is how fast the sequencer triggers each step. This in itself does not affect the length of individual samples so at extreme speeds loops will overlap in a densely fired texture or conversely there may be a lot of space and silence at very slow speeds. The last of the controls is volume of playback, which when used carefully can not only help to balance the live and processed material but can greatly increase the sensation of articulation and dialogue.

Within this framework the performer is free to improvise, guided by the constraints and freedoms of the instrument, themselves the hardware and software.

Enjoy

Video extract taken by Diane Evans at OscilloScope 28/6/15

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