Realizing Shepard Functions without the PAiA EK-9
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Author:  PAiA-Scott [ Fri Mar 05, 2010 2:28 pm ]
Post subject:  Realizing Shepard Functions without the PAiA EK-9

The manual for the EK-9 Shephard Function Generator experimenter's kit is newly posted over in the Documentation / Assembly Manuals section. The printed-circuit-boards for these are long gone, but if you want to try something like this, a MIDI Sequencer and multiple MIDI2CV8s (PAiA model 9700K) can be put to use for similar, perhaps even improved, results

Ideally, two MIDI2CV8s would be connected and operating in Control Change (multi-channel) mode with each output cv addressable, ie MIDI Channel 1 / MIDI2CV8 #1-Output #1, and so on, through the MIDI Channels and MIDI2CV8 outputs and ending on MIDI Channel 16 / MIDI2CV8 #2-Output #8. The Sequencer would then cycle or loop through MIDI Control Change Messages with numbers changing to cause the CV outputs to be Triangle and Ramp waves, offset in a time that is integral to the complete loop.

We'll say the Ramps are to MIDI2CV8#1 and the Triangles to MIDI2CV8#2 and the loop time is 80 seconds. The first channel of MIDI information is going to be 80 seconds of ascending MIDI continuous controller $0/#1 values, the next channel will be too, but beginning 10 seconds later. and so on, out to the eighth channel. At the same time the first channel's 'ramp' is beginning, the ninth channel's 'triangle' should begin. These triangle values with ascend for 40S and descend for 40S and, again, the eight channels are offset by ten seconds from each other.

One MIDI2CV8 could work with reduced resolution by programming the MIDI Sequence for four sets/channels of control change messages.

As the MIDI Sequence repeats, the MIDI2CV8 outputs will sweep through their ranges at their intervals with respect to the MIDI Sequence rate. With the Sequencer control you could even tailor the ramp or triangles to approximate exponential sweeps, or some other variation to the linear slopes of the ramp and/or triangle.

That gives the CVs if you had built an EK-9, but if you have a multi-timbral MIDI Instrument or sound-generator, you could bypass the cv realm and just go direct to the voice parameters with MIDI control.

If you try this, please share the results with us here.

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