My amp is playing a lot of radio stations at the same time.
The amp model is an Ibanez IBZ10Z, and it's plugged into my keyboard.
If the equipment is grounded, this could be a ground loop. (If you're using AC power and three-prong plugs, the third prong is the ground.) Try plugging the amp into a different outlet, one that's on a different circuit. They make ground loop isolators, but I don't know if they work or not; it might be worth investigating.
(I've used three-to-two-prong adapters to get rid of ground loop problems in a pinch, but I don't recommend it as more than a temporary solution. As per Owen's comments, it's quite dangerous to do this.)
This could be a potential answer to you question.
I was told one of the major reasons for balanced cables (note most guitar cables are unbalanced), is to prevent interference. Most notable is that of radio transmissions being picked up. The length of the cable relates to the frequency it will pickup, though your amp, or pickups could also pick up the signal.
Proper shielding, and shorter cables should solve the issue.
If your keyboard and amp can take a balanced cable investigate how to achieve this, as it should solve your issues.
If the extra noise is happening when you are playing the keyboard, make sure the Overdrive is turned off. Also, try plugging your guitar into the amp and see if it does the same thing.
If the extra noise is happening when you are not playing the keyboard, unplug the keyboard and see if it stops. Also, try adjusting all the knobs to see if anything changes.
If the noise is more like a buzzing sound, try @Neil Fein's suggestion about ground loops.