Someone please explain the steps to apply effects to electric guitar through the S975. I switched the input to guitar and, sure enough, the guitar plays nicely through that input. But, how do you apply the various effects, such as reverb, echo, distortion, overdrive, chorus, etc. I just get one basic sound that never changes. Is it possible to add guitar effects to guitar, or do those effects apply only to the onboard keyboard voices? I was hoping to apply the various effects to the guitar signal. But, despite all the button pushing, no luck.