Re: 'ello, keyboard problem...
The reason you can't control the keyboard at the amp is because you're using the "CD in", which is just meant for you to hook up a stereo to jam along to. I think that input bypasses the gain stage in the amp. You need to plug the keyboard into the main input on the amp. Forget the RCA cables. If the only output on the keyboard is the small headphone jack, you can run a cable that has the small (1/8" roughly) plug on one end, and the larger (1/4" roughly) at the other end.