Yamaha CS80

Hi All,

Does anyone know perhaps how Eddie Jobson gets that sweeping, morphing 
effect CS80 effect behind Allan Holdsworth's amazing guitar solo on In 
The Dead Of Night? It almost sounds like it's being arppegiated, but 
he's definately going back and forth between the 2 voices on the CS. 
This has had me stumped for years. I almost think it could be a quirky 
resonant hipass filter thing.

Thanks in advance,

Mark