This makes use of some interesting patching as well as VCF effects when the VCF ATTACK is longer than the VCF DECAY. Thanks to patching VCO 2 OUT to the VCA, it still produces some sound when not playing, which satisfyingly adds to the feeling of an engine idling, then various futuristic upshifts while playing.
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Fiddle with everything, you'll get some interesting sounds; the interplay between the TEMPO, VCF ATTACK, and VCF DECAY are where you find the the good stuff.