The first patch I made on a Buchla 100 was Douglas Leedy’s Entropical Paradise (1968). It was at the University of Pittsburgh in 1974. Frank McCarty was teaching there at that time, so it is likely I had the opportunity to patch his Stochastic Arp on the studio’s Arp 2500. Almost fifty years later, I can reconstruct both patches on a laptop using VCV Rack. Cool.
The scores for Entropical Paradise and Stochastic Arp can be found in Alan Strange’s Electronic Music: Systems, Techniques, and Controls , first published in 1972. While revisiting both works, I wondered if I could substitute the “stochastic arp” for the bird call. So, I gave it a try. I was liberal in my interpretation. My intent was not to mimic the Buchla and Arp patches exactly in VCV Rack.
The essence of the Entropical Paradise patch is described by J. Daniel Cramer in his Entropical Paradise Demonstration video (https://youtu.be/ocT5VqiYzog). There are two similar voices, each a VCO gated through a VCA using an envelope generator. The frequency of each VCO is controlled by mixing an eight- and a sixteen-step sequencer, respectively, with a stepped random voltage, one of which is inverted. Each voice has an LFO pulse generator which triggers the voice’s random voltage source and envelope generator. However, the LFO frequency is controlled by the other voice’s stepped random voltage source. Each voice’s sequencer is triggered by the other voice’s LFO pulse generator.
To add timbral variation to each voice, I added a low-pass filter to soften the sound. Also, I added random attack/decay variation to each voice’s envelope. The requisite reverberation occurs during mixing.
Stochastic Arp is essentially one voice: a VCO, run in series and parallel through band-pass filters and gated through a VCA using a compound envelope. The VCO frequency is controlled by mixing a smooth random voltage source with a stepped random voltage. The center frequencies of the band-pass filters are controlled with a mix of smooth random voltage and stepped random voltage. The amplitude of the compound envelope is a mix of a primary envelope generator, smooth random voltage, and a secondary envelope that is increasingly attenuated at random intervals. The stepped random voltage sources and the primary envelope generator are triggered by an LFO pulse generator whose frequency is controlled by one of the stepped random voltage sources.
During mixing, I added reverberation and random delay to the voice. These are not in the original patch.
Rather than let all three voices run mechanically (continuously and forever), I articulate the voices by gating them at random. This accentuates the interplay (if any) between the voices. Further, I randomly pan the voices between channels.
Strange stated that if you can work your way through both patches, you would be ready for just about anything. I’m not sure that statement anticipated encountering Stochastic Arp while in Entropical Paradise. Regardless, the result is, for me, a fanciful stroll down memory lane . . .
