This is a pair of Bucha 258J VCOs harmonizing with the Cocoquantus.  The 258Js go through a pair of cycling Haible Trapezoid VCAs into the Cocoquantus to be recorded.  And two of the Castle sample & hold outputs go back over to the FM inputs of the 258Js. The Cocoquantus performs amplitude modulation on the inputs coming from the 258Js, among other modulations.  Some twiddling occurred.